Archaeologists with Mexicos National Institute of Anthropology and History (INAH) have discovered an ancient Toltec altar and human remains near the Tula archaeological zone north of Mexico City. It dates to the Tollan period (9001150 A.D.) when Tula was the capital city of the Toltec Empire.The momoztli (altar) measures about one meter (3.3 feet) square and was built out of different stones, including volcanic blocks and river stone. It consists of three sections: a base of andesite quarry stone with small blocks no more than four inches thick on the outer face, a second section of larger slabs of andesite and a top section composed of river stones and basalt.Four skulls, one of them still connected to a vertebral column, and several long bones, probably femurs, were found placed on three of the four sides. Their placement suggests a ritual purpose, and archaeologists believe they may be the result of ceremonial decapitations. Ceramic vessels, including a black bowl containing another bowl, obsidian fragments, obsidian blades and bone tools, known to have been used in sacrificial rituals, were also found. Archaeologists also uncovered shell remains, spindle whorls and awls, objects that played roles in both ritual practices and daily life. The fourth side has not yet been fully excavated; there are likely to be remains there too.At the base of the altar were two skulls, one facing upwards and the other southwest. As the levels descended, a compacted layer with stucco, possibly lime and sand, was detected, and beneath this were found the other two incomplete skeletons, as well as some vessels.Heredia Guilln said there is little chance of finding complete skeletons, because perhaps only those parts of the individuals were offered as sacrifices. Once registered, they will be sent to the projects physical anthropology laboratory in the State of Mexico to determine age, sex, bone pathologies, and even whether they were decapitated, since one of the skulls still appears to be attached to the spine.In this case, although metals were already being worked in the Postclassic period, we know that here decapitations were still done with obsidian or flint knives, and they left cut marks on the bones, he explained.The altar was found near the Tula Chico area, about 300 meters (984 feet) from the perimeter wall of the Toltec capital. Remains of walls and foundations indicate the altar was in the center of a courtyard. INAH archaeologists believe the walls are the remains of elite buildings as people of high social rank in Tula lived outside the walls of the city.All of the artifacts and remains recovered from the excavation will be cleaned, conserved and studied in laboratory conditions. The bones will be analyzed to narrow down the date of deposition and to determine the individuals age, sex, geographical origins, health and possible causes of death.