It seems that every visitor to Mexico City at some stage heads out to the pre-Columbian pyramids at Teotihuacán (daily 7am–5pm): there’s a constant stream of tours, buses and cars heading this way, and the ruins are always amazing. It is an extensive site that can easily take up most of a day. It makes sense to plan ahead and it’s best to head out here as early as you can manage and do most of your exploration in the cool of the morning before the crowds arrive. From 11am to 3pm it can be very busy, and there is little shade, so you may want to spend that time at a restaurant or in the museum, returning refreshed for the photogenic light of the late afternoon. Visitors with limited Spanish will be glad to know that most of the explanatory signs are also in English. The ruins at Teotihuacán reveal a city planned and built on a massive scale, the great pyramids so huge that before their refurbishment one would have passed them by as hills without a second look. At its height this must have been the most imposing city in pre-Hispanic America, with a population thought to have been around 80,000 (though 200,000 is suggested by some sources) spread over an area of some 23 square kilometres (as opposed to the four square kilometres of the ceremonial centre). Then, every building grey hulks now would have been covered in bright polychrome murals. The main entrance, by Puerta 1, is at the southern end of the two-kilometre-long Calzada de los Muertos (Causeway of the Dead), which originally extended 1.5km further south, and formed the axis around which the city developed. A broad roadway some 40m wide and linking all the most significant buildings, it was built to impress, with the low buildings that flank most of its length serving to heighten the impact of the two great temples at the northern end. Other streets, leading off to the rest of the city, originally intersected it at right angles, and even the Río San Juan was canalized so as not to disturb the symmetry (the bridge that then crossed it would have extended the full width of the street). Its name is somewhat misleading, as it’s more a series of open plazas linked by staircases than a simple street. Neither is it in any way linked with the dead, although the Aztecs believed the buildings that lined it, then little more than earth-covered mounds, to be the burial places of kings. The design, seen in the many reconstructions, is fairly uniform: low three- or four-storey platforms consisting of vertical panels (tableros) supported by sloping walls. In many cases several are built on top of each other clearly demonstrated in the Edificios Superpuestos (superimposed buildings) on the left-hand side shortly beyond the river. Here, excavated structures underneath the present level may have been the living quarters of Teotihuacán’s priests.

Directly opposite the entrance at Puerta 1 lies La Ciudadela, the Citadel. This enormous sunken square, surrounded by stepped platforms and with a low square altar in the centre, was the city’s administrative heart, with the houses of its chief priests and nobles arranged around a vast meeting place. Across the open space stands a tall pyramid construction inside which, during excavations, was found the Templo de Quetzalcoatl. With the back of the newer pyramid demolished, the elaborate (Miccaotli phase) temple structure stands revealed. Pyramids aside, this is one of the most impressive sections of the whole site, rising in four steps (of an original six), each sculpted in relief and punctuated at intervals by the stylized heads of Quetzalcoatl, the plumed serpent, and Tlaloc, the rain god. Traces of the original paint can be seen in places. This theme with the goggle-eyed, almost abstract mask of Tlaloc and the fanged snake Quetzalcoatl, its neck ringed with a collar of feathers recurs in later sites throughout the country.

The great Pirámide del Sol (Pyramid of the Sun) is Teotihuacán’s outstanding landmark, a massive structure 70m high and, of Mexico’s ancient buildings, second in size only to Cholula. Its base is almost exactly the same size as that of the great Pyramid of Cheops in Egypt, but the lower-angled sides and its stepped nature make it very much lower. There are wonderful views from the top nonetheless, and the bulk is all the more remarkable when you consider the accuracy of its alignment: on two days a year (May 19 and July 25), the sun is directly over the pyramid at noon, and the main west façade faces the point at which the sun sets on these days. This alignment just off the cardinal points determined the line of the Calzada de los Muertos and of the entire city. Equally remarkable is the fact that the 2.5 million tonnes of stone and earth used in its construction were brought here without benefit of the wheel or any beast of burden, and shaped without the use of metal tools. In fact, the Pirámide del Sol, almost uniquely, was built in one go at a very early stage of the city’s development (about 100 AD), and there is only a very small older temple right at its heart. You approach by a short staircase leading to the right off the Calzada de los Muertos onto a broad esplanade, where stand the ruins of several small temples and priests’ dwellings. The main structure consists of five sloping layers of wall divided by terraces the large flat area at the top would originally have been surmounted by a sanctuary, long disappeared. Evidence of why this massive structure came to be raised here emerged in 1971 when archeologists stumbled on a tunnel (closed to the public) leading to a clover-leaf-shaped cave directly under the centre of the pyramid. This, clearly, had been some kind of inner sanctuary, a holy of holies, and may even have been the reason for Teotihuacán’s foundation and the basis of its influence. Theories abound as to its exact nature, and many fit remarkably with legends handed down through the Aztecs. It’s most likely that the cave was formed by a subterranean spring, and came to be associated with Tlaloc, god of rain but also a bringer of fertility, as a sort of fountain of life. Alternatively, it could be associated with the legendary “seven grottos”, a symbol of creation from which all later Mexican peoples claimed to have emerged, or to have been the site of an oracle, or associated with a cult of sacrifice in Aztec times the flayed skins of victims of Xipe Totec were stored in a cave under a pyramid.

At the end of the Calzada de los Muertos rises the Pirámide de la Luna (Pyramid of the Moon), a smaller structure built slightly later (but still during the Tzacualli phase), whose top, thanks to the high ground on which it’s built, is virtually on a level with that of the Pirámide del Sol. The structure is very similar, with four sloping levels approached by a monumental stairway, but for some reason this seems a very much more elegant building: perhaps because of the smaller scale, or perhaps as a result of the approach, through the formally laid-out Plaza de la Luna. The top of the pyramid offers the best overview of the site’s layout, looking straight back down the length of the central thoroughfare. It is perfect for sunset, though as it is then close to closing time the guards will soon chase you down. The Palacio de Quetzalpapálotl (Palace of the Quetzal-butterfly) lies to the left of the Plaza de la Luna, behind the low temples that surround it. Wholly restored, it’s virtually the only example of a pre-Hispanic roofed building in central Mexico and preserves a unique view of how the elite lived at Teotihuacán. The rooms are arranged around a patio whose elaborately carved pillars give the palace its name their stylized designs represent birds (the brightly coloured quetzals, though some may be owls) and butterflies. In the galleries around the patio several frescoes survive, all very formalized and symbolic, with the themes reduced almost to geometric patterns. Mural art was clearly very important in Teotihuacán, and almost every building has some trace of decoration. Two earlier buildings, half-buried under the palace, still have substantial remains. In the Palacio de los Jaguares, jaguars in feathered headdresses blow conch shells from which emerge curls of music, or perhaps speech or prayers to Tlaloc (who appears along the top of the mural); in the Templo de los Caracoles Emplumados (Temple of the Plumed Shells), you see a motif of feathers and seashells along with bright green parrots. Other murals, of which only traces remain, were found in the temples along the Calzada de los Muertos between the two pyramids.

Mural art was not reserved for the priests’ quarters – indeed some of the finest frescoes have been found in outlying apartment buildings. The famous Paradise of Tlaloc mural (reproduced in the Museo Nacional de Antropología) was discovered at Tepantitla, a residential quarter of the old city across the road from the back of the Pirámide del Sol. Only a part of it survives here, but there are others in the complex depicting a procession of priests and a ball-game. All have great vitality and an almost comic-strip quality, with speech bubbles emerging from the figures’ mouths, but their themes always have a religious rather than a purely decorative intent. More can be seen at Tetitla, to the west of the main site, and Atetelco, a little further west. Plan to spend at least some of your time in Teotihuacán’s excellent Museo del Sitio, situated behind the Pirámide del Sol and surrounded by a lovely sculpture and botanical garden. Artefacts from the site are well laid out and effectively lit to highlight the key features of each item in the cool interior. There’s just about everything you would expect of a ritual site and living city, from sharp-edged obsidian tools and everyday ceramics to some fine polychrome vessels decorated with animal and plant designs, and a series of five ceremonial braziers or censers ornamented with appliqué flowers, butterflies and shields. Vast windows framing the Pirámide del Sol take up one entire wall of the next room, where you walk across a glass floor look down to see a huge relief map of the entire city as it might once have been. This area leads to a second section mostly comprising larger sculptural pieces depicting assorted gods, often bottom-lit to accentuate the gruesome features. There are some superb masks, too, along with a couple of funerary sites modelled on those found under the Templo de Quetzalcoatl.

The rise and fall of Teotihuacán is almost exactly contemporary with imperial Rome. There is evidence of small agricultural communities in the vicinity dating to around 600 BC; by 200 BC a township had been established on the present site. From then until 1 AD (the period known as the Patlachique phase) the population increased, and the city assumed its most important characteristics: the great pyramids of the Sun and Moon were built, and the Calzada de los Muertos laid out. Development continued through the Tzacualli and Miccaotli phases (1–250 AD) with more construction and the blossoming of artistic expression. Then through the Tlamimilolpa phase (250–450 AD) there is evidence of the city’s influence (in architecture, sculpture and pottery) occurring at sites throughout modern Mexico and into Guatemala and Honduras. From 450 to around 650 AD (Xolalpan phase) it reached its peak in both population and power, with much new building and addition to earlier structures. Already by the end of this period, however, there were signs of decline, and the final phase, the Metepec, lasted at most a century before the city was sacked, burnt and virtually abandoned. This is thought to have been the result of attack by northern tribes, probably the Toltecs, but the disaster may in the end have been as much ecological as military. Vast forests were cut down to build the city (for use in columns, roof supports and door lintels) and huge quantities of wood burnt to make the lime plaster that coated the buildings. The result was severe soil erosion that left the hillsides as barren as they appear today. In addition, the agricultural effort needed to feed so many people (with no form of artificial fertilizer or knowledge of crop rotation) gradually sapped what land remained of its ability to grow more. Whatever the precise causes, the city was left, eventually, to a ruination that was advanced even by the time of the Aztecs. To them it represented a holy place from a previous age, and they gave it its present name, which translates as “the place where men became gods”. Although Teotihuacán features frequently in Aztec mythology, there are no written records – what we know of the city is derived entirely from archeological and artistic evidence, so that even the original name remains unknown.

On the way to the pyramids you pass a couple of places that are certainly worth a look, they can both be accessed easily by combi from a junction 500m beyond Puerta 5. At the village of Tepexpan is a museum (Tues–Sun 10am–4.50pm) housing the fossil of a mammoth dug up in the surrounding plain (then marshland). There’s also a skeleton known as the “Tepexpan Man”, once claimed to be the oldest in Mexico. This whole area is a rich source of such remains the Aztecs knew of their existence, which is one of the reasons they believed that the huge structures of Teotihuacán had been built by a race of giants. The museum is a fifteen-minute walk from the village, near the motorway tollbooths, where any bus will drop you. Buses to Metro Indios Verdes and combis to Teotihuacán can be picked up at the junction just outside the museum. A few kilometres towards Teotihuacán is the beautiful sixteenth-century convent of San Agustín Acolman (daily 9am–5.30pm). Built on a raised, man-made terrace (probably on the site of an earlier, Aztec temple), it’s a stern-looking building, lightened by the intricacy of its sculpted facade. In the nave and around the cloister are preserved portions of early murals depicting the monks, while several of the halls off the cloister display colonial religious painting and pre-Hispanic artefacts found here. If you turn right out of the gate, combis for Teotihuacán or Tepexpan can be picked up after 100m at the main road. Chiconcuac to the south is rather more of a detour, but on Tuesdays, when there’s a large market that specializes in woollen goods, sweaters and blankets, it’s included in the itinerary of many of the tours to the pyramids.