Tehuacalco, Archaeological site in Guerrero, Mexico.

Tehuacalco is an archaeological site near Chilpancingo, Guerrero, on a hill ringed by four mountains that mark the cardinal directions. Its ceremonial center covers twelve hectares and includes a 37.8-meter ball court, the 20-meter La Encinera pyramid, the Palace with an 80-meter base, and Platform W with elite residences and drainage systems.

Occupation began around 400 CE, with the site's height between 650 and 1100 CE, when the population center covered about eighty hectares and the ceremonial center twelve. Most structures were built while the Toltecs were at the height of their influence. The Yopes were sedentary farmers with rulers and priests at the top, followed by warriors, merchants and artisans. The Aztecs could not conquer the region, named Yopitzingo, in the late Postclassic; after the Spanish Conquest European diseases decimated the Yopes, whose major rebellion was crushed and survivors scattered.

The name Tehuacalco comes from Nahuatl tehuacalli, holes bored into stones for ritual use, and can mean "place of the stone box" or "house of the sacred water". The Yopes fed the sun, believed devoured by a monster each night, and honoured the mountains as stores of water and seeds. Look for the Piedra de los Pies Pintados, a rock carved with human footprints, and Monument W, whose circles counted lunar cycles.

The turnoff to the site is on the Mexico City–Acapulco highway near La Haciendita. The welcome center has explanations in Spanish, while the on-site signs are in Spanish and English. The hill paths are steep and uneven in places, so wear sturdy shoes and carry water.

The site's most sacred point is not a pyramid but a hill set aside as a sanctuary for the worship of water and rain. On the slopes of Cerro La Compuerta, 57 caves have been recorded, some holding offerings such as braziers and incense burners. The Yopes also treated the surrounding mountains as stores of water and seeds.