The main piece of Tula recognized by most visitors is its monumental center and main plaza known as Tula Grande. The plaza measures 130x150 meters (435x500 feet), and is surrounded by several monumental structures. Among these are two of the largest pyramids at Tula (Pyramids B and C), Buildings K and J, a skull rack (called by the Aztecs tzompantli), two ball courts and three additional buildings, including the so-called Palacio Quemado, with three painted friezes and the partially-excavated Palacio Quetzalcoatl.
The tzompantli was constructed from a rectangular platform, the remains of which included numerous fragments of human teeth and crania. Inside the platform was a large biface: opinions vary as to whether this was a Tula construction or an Aztec addition to Tula Grande.
Approximately 375 columns are included in the architecture of Tula Grande, most of which were square and built of stone masonry around a timber core. Many of these columns are elaborately carved in three dimensions, and many represent anthropomorphic and zoomorphic forms including serpents.
Architecture at Tula
Construction of the monuments at Tula include several characteristic elements, such as small-stone veneers, mortared onto the substructure with lime or mud and then covered with lime plaster. These veneers decorate altars, benches, columns, even some entire pyramids.
The substructure of the largest monuments typically is built of a framework of stone masonry filled with rubble or stacked courses of boulders or cobbles. Some have thick, elaborate adobe-brick walls of almost a meter (~3 ft) thick faced with lime plaster, stone veneer or paint.
The main portions of the buildings, and the free-standing sculptures, are carved from volcanic rock. Friezes are abundant, and represent processions of elegantly-attired rulers and warriors, but also canines, felines and raptors, and serpents munching on human skeletons.