Xochicalco is only site part of our pre-Hispanic past in Mexico, where we have such clear evidence of the advanced astronomical knowledge of its builders.

For Xochicalco builders observing the sky in the past thereby understanding the movements of each of the most luminous stars and applying it to their daily lives meant confirm the knowledge inherited from Teotihuacan builders.

Upon reaching the Xochicalco hill, having as its natural limit on Tembembe River towards which the sun sets, they were able to organize themselves to work collectively adapting the hill, creating large walls, enormous terraces, surrounded by temples and basements, which they used with different functions, from rituality, military, organization, protection and defense of the city. On the southern part of the indigenous city, they built a wall that guarded the main entrance to the city and dug deep moats, protecting a secondary entrance facing the east.

They left as evidence of their advanced astronomical knowledge about the annual movement of the sun, a horizon calendar in the Plaza de la Estela de los Dos Glifos, which was made with the construction in a special shape and measurements, where the sun rises, and allowed them to perform a daily time counting, preventing the arrival of significant dates in order to organize ceremonies, and agricultural process, such as preparing soles, planting , cleaning before the rainy season arrival, and perhaps the most precious moment: the harvest.

The ability to predict eclipses in the indigenous city of Xochicalco was materialized in an exemplary way in the most important building in the city, the Temple of the Feathered Serpents. In this building 8 feathered snakes appear carved in volcanic rock with impressive mastery, in which their plumes and beards can be appreciated over undulating bodies covered with feathers among it can see cut-out snails (commonly found in the area of the Gulf of Mexico) and precious beads, both expressions of the sacred. Among the snakes undulating bodies, on the facades located to the north, south and east, there are characters with recognizable Mayan features, in a meditative position. On the same facades of this building there are also represented, but in the upper part, characters from different places, whose characteristic they share is the observation of the sky (identified by the geometric headdress and blinders they wear, commonly recognized in the area of Oaxaca ), that is why they are determined as timekeepers, but all these characters came to Xochicalco at a moment defined by the stars: a total eclipse of the sun, possibly the first observed in this indigenous city in 664 AD, although there is a high probability that the subsequent total and annular eclipses were predicted, and seen from Xochicalco, especially the solar eclipses of the years 736, 743, 750, 790, and 797 AD. The sun eclipse occurred on July 16, 790 AD without a doubt was the most spectacular, and motivated the construction of the emblematic building in a well-established indigenous city of Xochicalco.

The record the eclipses was preserved on the Temple of the Feathered Serpents with a jaw that is about to eat a circle divided into 4 parts that represents the sun, that scene is repeated on three facades. On the west façade, the feathered serpents are shown with their heads meeting their tails and are surrounding, on one side, the representation of the calendar adjustment where the action of starting a new account can be seen, replacing the date with a zero in the day “10 house, year 6 cane” by the date “day 11 monkey”; this constitutes one of the most surprising legacies recorded at the site that can be seen nowadays.

The general interpretation of the set of reliefs and the construction of the temple itself is summarized: during a total eclipse of the sun seen in Xochicalco, people gathered from the Mayan area, from Gulf of Mexico coast, from Oaxaca and from various nearby places, in order to standardize the way of counting the time across the calendar.

These astronomical evidences, together with the pre-Hispanic Observatory, a natural cavern that was prepared by the city´s builders using a vertical shaft to be able to observe stars such as the sun, the moon, planets and constellations, make up the heritage value of this site that start from its architectural outline, its masterful artistic skill, its great engineering capacity to conduct water, its advanced astronomical knowledge, as well as its great defensive capabilities, taking advantage of the natural location during a socially complicated time known as Mesoamerican Epiclassic, more than 1300 years ago. Thus, giving meaning to the translation inherited from Xochicalco in the Nahuatl language, by the local residents themselves, as The House of the Flowering of Knowledge.