2 meters (7 ft) below the natural ground level, built on a base of yellow clay, dressed with travertine blocks. Four large, nearly identical, monumental travertine blocks adorn the east and west sides of the Sunken Patio. These blocks are carved to resemble anthropomorphic creatures, most likely were-jaguars, with almond-shaped eyes and down-turned mouths. In fact, it is these 3- to 5-ton monuments that are referred to in archaeologist Guadalupe Martinez Donjuán's name for the site, Teopantecuanitlan, Nahuatl for "place of the temple of the jaguar". According to Martinez Donjuán, these sculptures are situated so as to mark the equinoxes or solstices, and they "symbolized the opposing forces that ruled the world". The back of one of these monuments, Monument 2, contains symbols which Martinez Donjuán interprets as "10 Flower". If this interpretation is correct, this would be the oldest Mesoamerican calendar date yet discovered. This site also contains two ballcourts. One miniature ball court is located within the Sunken Patio itself while the other lies 900 m to the northeast. At one end of the smaller ball court there is an adobe sweat bath. This sweat bath was most likely used as a social bonding environment for the developing elite class of Teopantecuanitlan. Stone-faced patios and bas-relief monumental art are the features that are also found at the site of Chalcatzingo, Morelos. These are the only two sites known with these features. The sunken patio of Teopantecuanitlan is older. There are also other parallels between these sites. Other features Teopantecuanitlan is also home to the oldest known Mesoamerican dam. This dam was constructed around 1200 BCE and built of rough uncut rocks. This dam relied on gravity to bring water to the agricultural land. Canals, or channels, made of large flat stone slabs are also present in Teopantecuanitlan. The lining of these canals were of benefit to the domestication of plants by being a means of irrigation. These canals prevented erosion damage, loss of water also acted as a sewer. This site is also the first known within Mesoamerica to utilize the architectural feature known as a corbelled vault. This vault allowed for high ceilings without the use of trapezoidal cut stone. These corbelled vaults were used in ancient structures such as the tombs of the elite and in temples. Teopantecuanitlan society was not egalitarian — otherwise such monumental structures would not have been built. There was a leader