The substructure to Tula's pyramid was covered with thick white stucco, which may have symbolized the underworld.Although the temple at the top of the pyramid was destroyed, the stone columns that supported the roof still remain and were carved with images of Toltec warriors. Unique to Tula was the Coatepantli, or Snake Wall, a freestanding structure that encloses a passageway .north oflhe base of the pyramid. Both sides of
this passage consist of identical f iezes-top and bottom bands of geometrically stylized snakes framing the central panels and depicting partly skeletonized men apparently being devoured by serpents. Only two other coatepantlis are known to exist, those at Tenochtitlan and at Tenayuca, suggesting that they were a feature of Mesoamerica only from 900 to 1500.