mercoledì 16 marzo 2016

The Megalithic Ruins of Ancient Mexico - Part I

Megalithic Teotihuacan

Profile of  the main stairway of the pyramid of the feathered serpents in Teotihuacan, decorated with colossal serpent heads [Photo by Author]
               Mexico does not possess the impressive megalithic ruins of Peru and the Andes of South America, nor does it boast evidence of monumental architecture dating as far back as Caral and the other ceremonial sites in the Supe Valley of coastal Peru (dating as far back as 2,600 BC). Nevertheless, it certainly bears the footprints of equally enigmatic civilizations that prospered and vanished on its soil over several thousands of years, starting from the mysterious Olmecs, down to the Mayas, the Toltecs and finally the Aztecs.    
          
I have moved to Mexico last year from my natal country of Italy, and this has given me the chance to explore deeper the mysterious past of this ancient land.
Compared to the megalithic architecture of Peru, with its hair-tight joints and almost supernatural precision, ancient Mexican construction appears rather crude even in its most monumental expressions. For even the most impressive Maya pyramids, such as El Castillo of Chichen Itzá reveal a core of rubble and an outer casing of small quarried stones with loose joints, bound together with cement.
For this reason, it is even more so surprising to find among the rubble of dilapidated pyramids and temples some highly polished and perfectly finished megalithic stones. Almost invariably, these surprising megalithic findings do not seem to fit well with the rest of their surroundings, as if they belonged to an entirely different age and civilization.

Because of their apparent oddity, these megalithic remains have been largely ignored by the public and by specialists at large. Hardly a tourist stops in front of these strange megalithic relics, whenever they are not utterly inaccessible or restricted to visitors.
This is even the case in one of the most visited archaeological sites in the world, receiving as many as 100,000 visitors per day – Teotihuacan.

City of the Gods

               The ruins of what has been often called the Rome of America, Teotihuacan, lie a mere 50 Km North-East of modern day Mexico City.  At its peak, around 200 AD, Teotihuacan counted with a population of well over 125,000, hundreds of temples and palaces and three massive pyramids named after the Sun, the Moon and the Feathered Serpent (itself a symbol of the planet Venus). It is not my intention here to describe the ruins of this ancient city into any more detail than what is required by the subject of this brief dissertation – that is megalithic architecture in ancient Mexico.

The idea of starting a series of posts on megalithic architecture from a site which (rather obviously, even for the distracted tourist) does not boast any such examples would appear quite odd. Yet Teotihuacan does possess megalithic architecture, and on a colossal scale too; one just needs to walk slightly off the beaten path in order to find traces of it.  

For how impressive the Teotihuacan pyramids look from a distance, this impression of monumentality quickly dissipates as soon as one gets closer to the base or approaches the obligatory climb to the top. Not only are the pyramids not built of cut stone (and in this respect, they differ significantly from the Egyptian pyramids, to which they are so frequently equated), but they appear to consist of no more than cemented rubble and adobe (a kind of mud brick). That is, even if one ignores for a moment the rather imaginative early 20th century reconstructions.

But was it always the case?

The pyramid of the Sun as seen from the air, with the pyramid of the Moon in the background. The sheer impression of monumentality quickly vanishes as soon as one approaches the pyramid from close up. Unlike the Great Pyramid of Egypt, the Teotihuacan pyramids are not built of cut stone, but rather of a mix of cemented rubble and adobe. However, many hints suggest that they once similarly possessed a cut stone outer casing, which would have been later stuccoed and plastered to give it a smooth appearance. The pyramid of the Sun shares almost the exact same base measures as the Great pyramid of Giza, but has only half the height, resulting in a ratio of 4-´pi between the perimeter and the height. [Photo by Author]
Aerial photo of Teotihuacan, as seen from the Ciudadela. The pyramid of the feathered serpents is in the front, with the pyramids of the Sun and the Moon in the background. [Photo by Author]
Interestingly, Dupaix, one of the early pioneers of Mexican archaeology in the late 18th Century, and among the first to publish a sketch of the Teotihuacan pyramids in the West, still shows the pyramid of the Sun covered with a very regular cut stone casing (“revestido de piedras esquadradas” he would write in his report published a few years later). [1]

By the time Bullock visited the site in 1824, most of the casing stones were already gone, as he says that the outer faces of the pyramid were littered with pieces of “lime and cement…mixed with fallen stones”. He did however notice some “enormous stones” near the base of the great pyramid, including one “covered with sculptures” and another “with a hole in the middle”, which he suspected could have served as a sacrificial altar. [2]

Still to this day one finds several interesting stone blocks scattered in no apparent order around the main approach to the pyramid. Several of these carved stone blocks show very fine, polished surfaces, with sharp corners. Undoubtedly, they were once part of the outer casing of the pyramid of the Sun, and the ornamentations still visible on the stones portray the typical motifs of Teotihuacan art: figures of jaguars, circles, stars and sea shells.  

Several other finely carved stone blocks are scattered in a small sculpture park ("Parque escultorico") between the pyramid of the Sun and the Ciudadela - the vast walled compound that hosts in its center the pyramid of the feathered serpents. It is unclear where the stones originally belonged, but the variety of limestone, basalt, marble and even granite is quite impressive, as well as the very accurate finish of some of the stone blocks.

One needs however to reach the pyramid of the feathered serpents to find the first real and most compelling examples of megalithic architecture at Teotihuacan.

Detail of the ornamentation of the pyramid of the feathered serpents, with its characteristic serpent heads. From the picture above, it is possible to appreciate how far each stone extends inside the pyramid masonry. Each serpent head, including the body, is nearly 2 meters long and has an estimated weight of over 4 tons. [Photo by Author]
Another detail of the elaborate ornamentation of the pyramid, following the classic Talud-Tablero style of Teotihuacan architecture. The facade alternates serpent heads to giant masks interpreted to be the effigy of the rain-God Tlaloc, showing serpent-like as well as feline features. [Photo by Author]
The pyramid is today mostly hidden behind the so-called “adosada” platform, which was added to it towards the end of the 4th Century AD and covered much of the earlier structure. It was thanks to this later addition that the beautiful stone façade of the pyramid could be preserved along its western side, allowing a glimpse into how the Teotihuacan pyramids would have looked like had their stone casing been spared centuries of looting and quarrying.

The façade itself consists of beautifully carved stones, jointed and fitted together without mortar in the usual Teotihuacan Talud-Tablero style. The fantastic figures on its sides allude to the cosmic serpent, and alternate feathered serpent heads with masks of the god Tlaloc, amidst seashells and other marine symbols clearly related with water and the ocean (perhaps suggestive of the emergence of the sacred mound from the primordial waters of creation) In the few places where individual loose stones are visible, the very high quality of their workmanship can be fully appreciated, exhibiting sharp edges and perfectly planar surfaces unlike anything to be found elsewhere at Teotihuacan.   

In early February, I received from a friend some very intriguing pictures of large megalithic stones lying scattered in a vast area located immediately at the back of the Ciudadela and apparently coming from excavations conducted around the main pyramid itself. This area has now seemingly been fenced off, but was accessible at the time of this friend's visit in February.

To access it, one would need to walk along the entire perimeter of the Ciudadela until reaching its opposite (Eastern) side from the Avenue of the Dead. There, a ramp leads across the massive outer perimeter wall into the esplanade where the megalithic stone blocks are to be found.  

Not only are these possibly the largest stones ever to be found at Teotihuacan, but they are also the most finely cut and polished – to a level comparable to the ones forming the façade of the pyramid of the feathered serpents itself. 

As it can be seen from the pictures below, most of the stones are limestone and would have once formed part of a continuous façade not unlike the portion that is still preserved underneath the “adosada” platform.  Many of the larger stone fragments seem to belong to the familiar snake heads and masks that must have decorated the pyramid on each one of its four sides, but others also bear decorations of a different kind - not found on the other sides of the pyramid wherever its sculptured decoration has survived the ravages of time.

What is perhaps most striking is that these examples of megalithic architecture are almost invariably found in the oldest layers of construction of the ancient metropolis, and we would not rule out the possibility that they might have once formed part of even older, now vanished megalithic structures – perhaps later reemployed by the builders of Teotihuacan of the historical period for their constructions.

An overview of the area behind the pyramid of the feathered serpents, with many of the large megalithic stone blocks lying scattered around its base, each one weighting multiple tons. [Copyrighted picture - No reproduction allowed]
A detailof the state in which many of the stones are to be found, partially embedded in the now demolished filling of the "adosada" platform. Not the curious U-shape of some of the larger blocks. [Copyrighted picture - No reproduction allowed]
More megalithic stone blocks scattered around the base of the pyramid, some of which bearing the same ornamentation as the blocks found on the main facade of the pyramid, to the sides of the monumental stairway. See for instance the large serpent head in the foreground. [Copyrighted picture - No reproduction allowed]
Some of the stones appear to be badly eroded or deliberately damaged, while others exhibit perfectly smooth surfaces and straight angles. One is left to wonder as the reason why these stones ended up being scattered and reused in the filling of the "adosada" platform. [Copyrighted picture - No reproduction allowed]
Echoes of the fifth sun

In the legends and myths of the Aztecs, Teotihuacan was the place where the gods convened to give birth to the Fifth Sun of our era, after a previous world age had ended in darkness. It is in that remote age that we need to look for the unknown megalithic builders of Teotihuacan.

According to a story that was told and copied by Bernardino de Sahagún soon after the conquest:

They say they came to this land to rule over it…they came from the sea on ships, a multitude of them, and landed on the shore of the sea, to the North…from there they went on, seeking the white mountains, the smoky mountains…led by their priests and by the voice of their gods. Finally they came to the place that they called Tamoanchan…and there they settled for some time…but it was not for long, for their wise masters left, took again to their boats…bringing back with them all their holy books and their sacred images[3]

If we are to believe the informers of Sahagún, the builders of Teotihuacán-Tamoanchan had come from the sea, and had brought with them the principles of all arts and sciences. Did they also bring knowledge of megalithic architecture with them?

The beginnings of Teotihuacan are obscure. Monumental architecture on the site sprung almost immediately, in a single spree of construction that resulted in the general layout of the site as we appreciate it today, with its three main pyramids distributed along the 3-miles stretch of the Avenue of the Dead.     

New constructions were added on top of the older, but always following the same grand plan drawn by the original unknown founders of the city, perhaps centuries or even thousands of years earlier.

Perhaps these scattered megalithic remains are all that is left of the original City of the Gods.

References:
[1] From a Drawing in BNAH, inv. 58, 21x30.7 cm
[2] William Bullock, Six months Residence and Travel in Mexico, p. 416 (London, J. Murray, 1824)
[3] Bernardino de Sahagún, Codice Matritense de la Real Academia, folio 191,192

A detail of a large monolithic serpent head from a complex of buildings along the Avenue of the Dead. All over Teotihuacan and ancient Mesoamerica, the most sophisticated architecture is always found in the lower occupational layers. In this case, the floor level was raised when a new platform was built on top of the already existing one, thus covering and preserving its beautiful stone ornamentation. [Photo by Author] 
From this other perspective of the same building, it is easy to appreciate how the older construction (below the later floor level) exhibits a much superior workmanship and architectural technique, with the use of larger, sometimes even megalithic stones. [Photo by Author]
One of many architectural fragments preserved in the "Jardin Escultorico" of the site. This one in particular bears a very elaborate ornamentation and might have been part of a larger sculptured monolith, of which it is the only surviving fragment. [Photo by Author]
More interesting sculptural fragments from the "Jardin Escultorico". This one is carved in a way similar to the crown of feathers placed around some of the giant serpent heads that decorate the facade of the pyramid of the feathered serpents, a few hundred meters to the South. [Photo by Author]
Slightly off the beaten path, one finds literally hundreds of fragments of sculptures, with varying degrees of finish and polish. Unfortunately there is no information provided on the provenance of these fragments. [Photo by Author]
Some of the architectural fragments aligned on one side of the inner courtyard of the Ciudadela, near the pyramid of the feathered serpents. [Copyrighted picture - No reproduction allowed]
More of the elaborately carved stone blocks lying in the courtyard of the Ciudadela. Not the very fine polish and finish of some of the larger stones in the foreground. [Copyrighted picture - No reproduction allowed]
This picture, taken from one side of the pyramid of the feathered serpents, clearly shows the exposed nucleus of the pyramid , with its elaborate architectural ornamentation, with the remains of the "adosada" platform clearly visible to its left. The empty space between the two is a result of  20th Century restorations. [Copyrighted picture - No reproduction allowed]
A particular of the sculptured decoration of one of the outer faces of the pyramid of the feathered serpents, where large and carefully fitted stone blocks are clearly visible embedded in the more incoherent masonry that constitutes the core of the pyramid. [Copyrighted picture - No reproduction allowed]
Some of the large megalithic stone blocks lying in the esplanade behind the pyramid of the feathered serpents. Not the large serpent head and body in the foreground, as well as the many other beautifully carved and sculptured stone blocks. [Copyrighted picture - No reproduction allowed] 
Another view of the chaos of megalithic stones lyng around the base of the pyramid of the feathered serpents. [Copyrighted picture - No reproduction allowed]
Of the several sculptured fragments lying around the base of the pyramid, many are found still partially embedded in the masonry fill of the pyramid, as if they had been simply dumped there after the demolition of the original construction. [Copyrighted picture - No reproduction allowed]
This enormous stone, one of the largest on the site, was probably part of a continuous frieze. No similar ornamentation exists on any one of the other preserved stone blocks that decorate the main facade of the pyramid. This stone might belong to an entirely different construction. Perhaps it formed part of the temple that would have originally stood on top of the pyramid and of which no other trace survives to this day. [Copyrighted picture - No reproduction allowed] 
Even this comparatively small fragments shows the very fine quality and workmanship of some of the stones, all apparently carved in complex tridimensional patterns as part of a gigantic architectural composition. [Copyrighted picture - No reproduction allowed]
A curious mask carved on a large megalithic stone block. An almost identical carving is found in the site Museum of Teotihuacan. [Copyrighted picture - No reproduction allowed]
More of the very large megalithic stone blocks still lying in their original position  where they were dumped into the masonry fill of the "adosada" platform (now demolished). Are we looking at the remains of deliberate destruction, a kind of damnatio memoriae, or was perhaps a cataclysm responsible for the collapse and ultimate abandonment of these structures? [Copyrighted picture - No reproduction allowed]
Another view of the same area with more of the large megalithic stone blocks still partially embedded in the later masonry fill of the pyramid. [Copyrighted picture - No reproduction allowed]
Particular of a stone block with a motif resembling a crown of feathers or petals like the ones that encase the serpent heads placed on the main facade of the pyramid. [Copyrighted picture - No reproduction allowed]
Another of the large U-shaped stone blocks lying above a broken serpent head still embedded in the later masonry fill. The serpent head block would have originally been inserted amidst two U-shaped stone blocks forming a crown around it. [Copyrighted picture - No reproduction allowed]  
Particular of a stone block with a motif resembling a crown of feathers or petals like the ones that encase the serpent heads placed on the main facade of the pyramid. Note the very fine workmanship of the tridimensional pattern on the stone. [Copyrighted picture - No reproduction allowed]
Another view of the chaos of megalithic stones lyng around the base of the pyramid of the feathered serpents. [Copyrighted picture - No reproduction allowed]
Another view of the chaos of megalithic stones lyng around the base of the pyramid of the feathered serpents. [Copyrighted picture - No reproduction allowed]
Particular of one of the few other areas of cut stone architecture at Teotihuacan, this time a stairway leading to a palatial building on one side of the Avenue of the Dead, near the Plaza of the Moon. The quality of the stone architecture visible here is a very sharp contrast to the poor construction of the building behind. An older layer of construction is also visible in the background under the later masonry filling. [Copyrighted picture - No reproduction allowed] 

sabato 1 agosto 2015

The Pyramid Network - Part I, The Valley of Mexico

Part I - The Valley of Mexico
An overview of the system of alignments of ancient sites that we have discovered across the Valley of Mexico. The great Aztec capital of México-Tenochtitlan occupies the most privileged spot in this scheme, at the intersection of two major alignments. Texcoco, Chapultepec, Tenayuca and Cerro de la Estrella represent equally important focal points in the same scheme. [Reconstruction by Author, courtesy Google Maps]
                “A great, scientific instrument lies sprawled over the entire surface of the globe. At some period, thousands of years ago, almost every corner of the world was visited by people with a particular task to accomplish. With the help of some remarkable power, by which they could cut and raise enormous blocks of stone, these men created vast astronomical instruments, circles of erect pillars, pyramids, underground tunnels, cyclopean stone platforms, all linked together by a network of tracks and alignments, whose course from horizon to horizon was marked by stones, mounds and earthworks”

[John Michell, The New View over Atlantis, Thames & Hudson, Reprinted 2001]

                This is the first part of a series of articles on what will be considered by many as a very controversial subject. The topic is that of the alignment and placement of ancient sites. There are many theories and speculations on why a particular location was chosen for the placement of ancient pyramids, ancient temples and sanctuaries, ranging from Giza’s Orion correlation theory to New Age beliefs in the existence of such things as ley lines and Earth energies.

A number of studies and the advances in the still relatively new discipline of archaeoastronomy have revealed important elements of the connection between the ancients and the Sky. Nevertheless, when this approach is applied outside of a single site or landscape feature to encompass multiple ancient sites (as in the case of the Egyptian pyramids or the ancient city of Angkor, in Cambodia), the results are, at best, controversial.
Even more controversial is the idea that the placement of ancient sites, even over very long distances, would be ruled by geodetic or mathematical proportions having little or no connection at all with the local geography or other strategic reasons usually advocated for explaining the location chosen for the founding of a city or a temple.

Geodesy, that is the science of measuring of the Earth, is not something commonly ascribed to ancient civilizations. The accurate determination of latitude and longitude has only been possible in relatively modern times, with the invention of precision chronographs. While latitude can be calculated with sufficient accuracy with the help of a quadrant or astrolabe, by observing the altitude of the sun or of certain “fixed” stars above the horizon, the problem of longitude remained without a solution until the invention of the marine chronometer in 1773. [1]

Without such knowledge, establishing a “grid” or network of ancient sites over a large enough area would have been highly unpractical, if not impossible. This is why such a theory of long-distance alignments of ancient sites – which would moreover need to take into account the curvature of the Earth or some advanced surveying and projection techniques believed to be the exclusive domain of modern science -  is nowadays utterly dismissed as a wishful fantasy.

This often turns into a circular argument. Because no ancient civilization clearly possessed the scientific or technological instruments required to achieve such precision alignments, then any alignment must be the product of chance or coincidence. This is, not to speak of the reason why ancient civilizations should have deliberately placed their sacred sites along a grid or system of geodetic and landscape alignments of some sort. More on this later.

Three Pyramids and a “Star” Mountain
This was the likely aspect of the great Aztec capital of México-Tenochtitlan at the time of the arrival of the Spanish Conquistadores in 1519. A city of 250,000, larger than any Western European city at the time, built on an island in the middle of the lake of Texcoco. Its ruins lay buried underneath present day Mexico City, while even the lake has succumbed to the growth of the modern-day Mexican capital. [La Gran Tenochtitlan, original painting by Miguel Covarrubias, Museo Nacional de Antopologia, Mexico City]
                Ancient Mexico is an excellent ground for the study of ancient alignments. Not only do we find a continuity of civilization and beliefs going back thousands of years, from the Aztecs, Toltecs, Maya and Teotihuacan, down to the mysterious Olmecs; but we also find more pyramids than in any other Country in the world to verify such a theory (there are no accurate estimates, but the number might easily be in the thousands).  
The Valley of Mexico, with its vast flat plain once occupied by the ancient lake of Texcoco and surrounded by high mountains, will be the perfect setting to verify our theory of alignments.

When drawing on a map the major ancient sites around the Valley of Mexico, almost immediately an interesting pattern starts to emerge. 
There are three major Aztec pyramids within the boundaries of present day Mexico City: these are the Templo Mayor of México-Tenochtitlán, the Templo Mayor of Tlatelolco and that of Tenayuca.

All these constructions share very similar characteristics: they were built around the same time period, between the XIV and the early XVI Century AD, and were all subject at some point to Aztec rule, erected by people sharing a similar system of myths and beliefs. They all consist of a large pyramid platform, surmounted by a double sanctuary and enclosed within a sacred precinct. Let me state this again: These are the three largest pyramids within present day Mexico City, and are virtually identical in construction and design [2]; yet, no one has apparently noticed (up to this day), that they are also very precisely aligned among each other.

Let’s take a closer look:

Tenochtitlán 
A model reconstruction of the Templo Mayor of México-Tenochtitlan, from the Museo del Templo Mayor. One of the major archaeological discoveries of the 20th Century, this ancient pyramid had laid buried for almost 500 years underneath one of Mexico City's busiest squares. Excavations began in 1978, and are still ongoing. [Museo del Templo Mayor, Mexico City]
                The great Aztec capital of Tenochtitlán was built on an island in the center of the lake of Texcoco, subsequently enlarged with the construction of artificial dykes and canals. At the very center of the City, within the sacred precinct, was the great Teocalli, the Templo Mayor, with its twin sanctuaries dedicated to the gods Tlaloc and Huitzilopochtli. Built as a massive pyramid, the temple had at least seven stages of construction, dating from 1337 to 1521 AD. At its peak, the temple measured 100 by 80 meters at its base, and reached between 45 and 60 meters in height. Its impressive ruins, discovered in 1978 after centuries of abandonment and deliberate destruction, are still one of the major tourist attractions in downtown Mexico City.    

Tlatelolco
The ruins of Tlatelolco, in present day Plaza de las Tres Culturas. Archaeological excavation have revealed the main ceremonial center of the city that was the sister twin of México-Tenochtitlan and rivaled with it in power and splendor. [Photo by Author]
After the conquest, the Spanish built a large church and a convent, named after the Colegio de Santa Cruz, on the site of the former Templo Mayor of Tlatelolco. The ruins of the massive pyramid still bear evidence of several layers of construction, being almost identical to the Templo Mayor of México-Tenochtitlan. [Photo by Author]
                Tlatelolco was a sort of sister city to México-Tenochtitlán, also built on an island in the lake of Texcoco. The city itself was founded by a dissident Aztec faction only 13 years after the founding of México-Tenochtitlán, in 1338 AD. Like the Templo Mayor of its sister city, also the great pyramid of Tlatelolco underwent several construction stages – at least seven, whose imposing ruins still survive in what is today Plaza de las Tres Culturas. The last construction stage had similar dimensions to the Templo Mayor of México-Tenochtitlán, measuring some 80 by 70 meters at the base, and also included a double sanctuary at the top dedicated to the gods Tlaloc and Huitzilopochtli.  

Tenayuca
The great pyramid of Tenayuca is one of the best preserved constructions of the post-classic period in the valley of Mexico. The massive pyramid also contains the remains of at least 7 other earlier stages of construction. The great pyramid of Tenayuca, with its twin sanctuaries and double stairway is considered the prototype for both the Templo Mayor of México-Tenochtitlan and of Tlatelolco. [Photo by Author]
The base of the pyramid of Tenayuca is surrounded by a massive Coatepantli, that is, a "wall of snakes", which incorporates as much as 140 sculptured serpent heads. These sculptures were originally painted in bright colors, to indicate the different cardinal directions. [Photo by Author] 
                Tenayuca was an old settlement of the Chichimecas, whose foundation might be traced back to as early as 1064 AD. The last stage of construction of this pyramid, which was likely the prototype of all later Aztec pyramids, measured 68 by 76 meters at its base, and also underwent several stages of construction and reconstruction (at least eight). Also at Tenayuca, a twin stairway led to the double sanctuary on top of the massive pyramid.  Interestingly, the pyramid of Tenayuca does not share the same equinoctial orientation as the Templo Mayor of México-Tenochtitlán and Tlatelolco, but is rather oriented towards the setting of the star Aldebaran, in the constellation of Taurus, 17 degrees north of the ideal East-West orientation on the day of the passing of the Sun at its zenith. [3]

The Alignment Tenayuca – Tlatelolco – Tenochtitlán – Cerro de la Estrella
The main system of ancient alignments around the Templo Mayor of México-Tenochtitlan. [Reconstruction by Author, courtesy Google Maps]
                It is easy to realize that a line drawn through the summit of the Templo Mayor of México-Tenochtitlán and the Templo Mayor of Tlatelolco would terminate exactly on the main sanctuary of the pyramid of Tenayuca.

To further confirm and reinforce the existence of this alignment, it should be noted that one of the major road arteries in present day Mexico City, the Calzada Vallejo, follows exactly this same alignment between Tlatelolco and Tenayuca. This is not surprising, given that the modern road follows the track of one of the ancient causeways that crossed the – now dry - lake of Texcoco in Aztec times.

A detail of the alignment along the Calzada Vallejo, which follows a straight line that would have originally connected the Templo Mayor of México-Tenochtitlan to the great temple-pyramids of Tlatelolco and Tenayuca. Note also the right triangle formed between Chapultepec, Tenayuca and Texcoco. [Reconstruction by Author, courtesy Google Maps]
A prolongation of this alignment towards the South-East also leads to another very important landmark in Mexico City. This time, it is not a pyramid, but rather a steep, forested hill called Cerro de la Estrella. Again, this can be no chance: The Cerro de la Estrella played a very important role in the sacred geography of the Valley of Mexico, as it is the spot where the Aztecs celebrated the New Fire ceremony every 52 years, at the end of each calendar cycle and the beginning of a new one. 
The etymology of the name is unclear; Cerro de la Estrella meaning “Mountain of the Star”, supposedly after a colonial hacienda by the same name built on its slopes soon after the Spanish conquest of Mexico. The ancient name of the hill, which rises 224 meters above the surrounding plain, was Huizachtecatl, meaning a forested hill in ancient Nahuatl. Yet the highly evocative name of “Mountain of the Star” could have a much more profound astronomical significance that we do not yet fully understand.

A pyramid was built by the Aztecs on top of the Cerro de la Estrella, but the occupation of the site dates back at least 3,000 years. A large settlement occupied the slopes of the hill between 100 and 650 AD, contemporary with the rise of the power of Teotihuacan in the valley of Mexico, on the North-Western shore of the lake of Texcoco.

Interestingly, the alignment would not appear to point towards the summit of the hill, but rather deviates a couple of degrees to the West towards a little eminence on its Western slope.
In 2006, a massive pyramid was discovered on the Northern slopes of Cerro de la Estrella, measuring as much as 150 meters at its base, one wonders what might still lie buried at this fascinating site. [4]

The picture expands
The two major systems of alignments that cross modern-day Mexico City - the line Tenayuca-Tlatelolco-Tenochtitlan-Cerro de la Estrella and the line Chapultepec-Tenochtitlan-Texcoco cross at a right angle on the site of the great pyramid-temple of México-Tenochtitlán, as can be easily verified from the picture above. [Reconstruction by Author, courtesy Google Maps]
                For how interesting the alignments we have discovered so far, these would have been certainly within the technical capabilities of the Aztecs: The longest distance in the alignment, that is the one between Tenayuca and Cerro de la Estrella, is only 22.5 Km, meaning that the hill would have been within a clear line of sight connecting Tenayuca to the great temples of Tlatelolco and Tenochtitlán. This was even truer in ancient times, without the pollution and haze of modern day Mexico City.

Interestingly, the Templo Mayor of Tenochtitlan is located exactly at the same distance of 11.3 Km from Tenayuca and Cerro de la Estrella, being at the exact center of the imaginary line connecting these two points (1:1). 
And what about the position of Tlatelolco? The great pyramid of Tlatelolco is located only 1.9 Km from the Templo Mayor of Tenochtitlán. That means, Tlatelolco divides the line connecting the pyramid of Tenayuca to that of Tenochtitlán in two segments of 1.9 and 9.4 Km; the total segment length being 11.3 Km. This means that the distance Tenochtitlán-Tlatelolco is exactly 1:5 of the distance Tlatelolco-Tenayuca. 

And there is more. This first alignment Tenayuca-Tlatelolco-Tenochtitlán-Cerro de la Estrella appears to be at a right angle with another equally impressive alignment, also crossing through the Templo Mayor of México-Tenochtitlán.

The alignment Texcoco-Tenochtitlan-Chapultepec

This second alignment connects the ancient city of Texcoco to the sacred hill of Chapultepec, and in doing so crosses the axis Tenayuca-Cerro de la Estrella at a right angle exactly in its center, that is on the spot occupied by the Templo Mayor of México Tenochtitlán.

The Cerro de Chapultepec, whose summit is now occupied by the castle built for Emperor Maximilian I of Mexico in the XIX century, was considered sacred by the Aztecs. There the Aztec emperors had their baths and gardens, and a temple likely existed on the summit. Several astronomical and geodetic markers are still to be found on the high cliffs below the castle, including some fine bas-reliefs of Moctezuma II and a giant rock sculpture of a snake.

On the opposite end of the alignment, Texcoco was one of the cities of the Aztec triple alliance, together with México Tenochtitlan and Tlacopán (Tacuba). A city of the Acolhuas, Texcoco became one of the most important cities in ancient Mexico during the reign of Netzahualcoyotl, extending itself over 450 hectares on the shores of Lake Texcoco. The city became a major center of learning, and has been often described as the “Athens” of ancient America; home of poets, philosophers and astronomers, as well as to one of the largest libraries of the pre-Columbian world. The great temple of Texcoco was apparently second only to the one of México-Tenochtitlan, and the legendary palace of Netzahualcoyotl, consisting of some 300 rooms and all built of dressed stone, was still a wonder to behold at the time of Bullock’s visit in 1824. [5]  
An ancient depiction of the Templo Mayor of Texcoco, with its twin sanctuaries at the top, from the Codex Ixtlilxochitl , early 16th Century [Codex Ixtlilxochitl, fol. 112V]
Very little remains nowadays of the former glory of Texcoco. The last remnants of the great temple of Texcoco were demolished sometime around 1880 to make material for construction, but its location is accurately marked in XIX century maps at a place known as “Cerro de La Simona”, along the present day Calle Guerrero, and between the Calles Allende and Aldama. This position allows drawing a precise alignment between the Templo Mayor of Texcoco and the Templo Mayor of México-Tenochtitlan, pointing to the sacred hill of Chapultepec (itself a major natural landmark on the immediate shores of what was then the lake of Texcoco).

The alignment Texcoco-Cerro de la Estrella-Cerro del Ajusco

Something very interesting also happens when observing the alignment between Texcoco and the Cerro de la Estrella. A prolongation of this line points straight to the summit of the Ajusco; the highest peak, with its 3,930 meters, within modern Mexico City boundaries and one of the most easily recognizable landmarks in the entire valley of Mexico (its highest point, called Pico del Aguila or Eagle’s peak was considered sacred since ancient times, and does indeed resemble a giant spread eagle from the distance).

The triangle Texcoco-Teotihuacan-Mount Tlaloc

Texcoco is also at the vertex of an isosceles triangle, that if forms with the ancient sacred sites of Teotihuacan and Mount Tlaloc. The distance between Texcoco and Teotihuacan and between Texcoco and the summit of Mount Tlaloc is the same and equals 12.5 Km. This is suggestive of a system of survey points or triangulation markers.

Teotihuacan was one of the major ceremonial centers of the classic period in the valley of Mexico, a city whose influence extended as far as Guatemala and the Maya region. On the other hand, Mount Tlaloc, with its 4,151 meters, is one of the highest points in the valley of Mexico, and a sacred mountain connected with the cult of the rain-god Tlaloc. The pre-Hispanic sanctuary on its summit is believed to be the highest archaeological site in the world, and consists of an imposing platform approached by a stone causeway, from whose summit the view easily embraces the entire valley of Mexico and beyond.

Connecting the dots  
The two interconnected systems of alignments centered on the Templo Mayor of México-Tenochtitlan and on the great pyramid-temple of Texcoco. The lines in black are hypothetical lines of sight drawn from the holy city of Teotihuacan and the pre-Columbian sanctuary on the summit of Mount Tlaloc. These two points are equidistant from Texcoco. The apparently arbitrary placement of the Templo Mayor of Tlatelolco along the axis Cerro de la Estrella-Tenochtitlán-Tenayuca now becomes clear once a new line of sight is drawn from Teotihuacan to the Cerro de Chapultepec. [Reconstruction by Author, courtesy Google Maps]
After connecting all the dots, the resulting figure resembles an enormous kite, having at its four vertices the sacred sites of Texcoco, Tenayuca, Cerro de la Estrella and Chapultepec. The observation points of Cerro del Ajusco, Monte Tlaloc and Teotihuacan remain outside of this figure, but are placed symmetrically with respect to each other and to the overall figure on the ground. The Templo Mayor of México-Tenochtitlan occupies the center of this scheme, at the intersection of the two major alignments.

It is interesting to note that while the location of the great temples of Texcoco, Tenayuca, Tenochtitlan and Tlatelolco, as well as of the sacred city of Teotihuacan, reflects a deliberate artificial construction, the natural landmarks of Chapultepec, Cerro de la Estrella, Mount Tlaloc and Cerro del Ajusco are prominent landscape features over which human design could have had no role.

It was probably from the observation that the remarkable hill of Cerro de la Estrella lies virtually at the center of the triangle formed by three other major natural landmarks: the Cerro de Chapultepec, Cerro del Ajusco and Monte Tlaloc, that the position of all the other sites could be determined. 

The prominent role of Teotihuacan in this system of alignments suggests that at least part of this design might date back to the time in which the great city exerted its dominion over all of Central Mexico (that is, at least in the 2nd Century BC), a time therefore much earlier than that of the Aztecs.

The location of the great temple and the city of Texcoco was likely defined relative to that of Teotihuacan (which already existed at the time), of Mount Tlaloc, Cerro de la Estrella, Cerro del Ajusco and Chapultepec. This location is almost “miraculous” in that it is exactly equidistant between Teotihuacan and Mount Tlaloc, and is also found on the prolongation of the natural alignment between the Cerro del Ajusco and Cerro de la Estrella.

The position of the Templo Mayor of México-Tenochtitlan was subsequently defined along the line of sight between Texcoco and Chapultepec, in such a way that it would perpendicularly intersect a line drawn through the Cerro de la Estrella and to Tenayuca.

The location of Tlatelolco is even more interesting, in that it is situated along the axis Cerro de la Estrella – Tenochtitlan – Tenayuca, and also marks the point in which a line of sight drawn from Teotihuacan to the Cerro de Chapultepec intersects this latter axis.

The final picture of all the major alignments and lines of sight discussed in the present article. The major triangles and geometric figures are highlighted in different colors. The base of the triangle having Texcoco as its center (highlighted in red), marked by the axis Chapultepec-Mount Tlaloc, corresponds to the parallel of latitude at 19° 25´ North. Tenayuca and Cerro de la Estrella are also at the center of two other large triangles (in green), with the Templo Mayor of México-Tenochtitlan located at the (perpendicular) intersection of the lines connecting the centers of these 3 geometric figures. [Reconstruction by Author, courtesy Google Maps]
This systems suggests a very advanced (for the time) knowledge of cartography and trigonometry for the purpose of triangulation, and also highlights the existence of a network of alignments of sacred sites based on ancient lines of sight, which has surprisingly gone virtually unnoticed for the past 500 years. It also suggests that the location chosen for some of the major temples and ancient cities in the valley of Mexico, including the very Aztec capital of México-Tenochtitlan, is not arbitrary, but rather the product of an elaborate geodetic scheme that incorporates pre-existing natural as well as artificial landmarks. 

References

[1] The Board of Longitude, established in 1714, rewarded John Harrison for the invention of the marine chronometer in 1773. Before that, longitude could only be crudely determined with the so called “Lunar distance method”, first devised by Galileo Galilei in 1612, who noticed that the relative positions of the Moon and Jupiter could be used as a sort of universal clock; a method which however required accurate knowledge of their orbits and cycles.  
[2] The chief archaeologist and director of excavations at Tlatelolco, Salvador Guilliem, even goes to the point of suggesting that these three pyramids, those of Tlatelolco, Tenayuca and Tenochtitlán, bear such close similarities to each other that can only be explained if they were erected by the same builders.
Descubren en Tlatelolco Pirámide más antigua que Tenochtitlán, in La Jornada, 27/12/2007, accessed on-line: http://www.jornada.unam.mx/2007/12/27/index.php?section=cultura&article=a04n1cul
[3] Enrique Juan Palacios, La Orientación de la Pirámide de Tenayuca y el principio del año y siglo indígenas, Contribución al XXV Congreso de Americanistas de la Plata, Buenos Aires, 1932. Accessed on-line: http://www.revistadelauniversidad.unam.mx/ojs_rum/files/journals/1/articles/4006/public/4006-9404-1-PB.pdf
[4] Massive Ancient Pyramid Discovered in Mexico, The Guardian, 4th May, 2005. Accessed on-line: http://www.nbcnews.com/id/12173346/ns/technology_and_science-science/t/massive-ancient-pyramid-discovered-mexico/#.VaWZ2qRViko
[5] William Bullock, Six Months Residence and Travels in Mexico, London, 1824, p. 383-395