The Tomb of the High Priest or Osario Temple is a step-pyramid temple with staircases on each side. The temple stands atop a natural limestone cave in which skeletons and offerings were found, giving the temple its name. Archaeologists today believe the structure was neither a tomb nor that the personages buried in it were priests. The temple shows combined Toltec and Puuc characteristics, and shows a striking resemblance to El Castillo. It has 7 levels instead of the 9 of its larger counterpart. The pyramid itself is about 30 feet (9 meters) high with 4 stairways on each side, with a sanctuary in the center and a gallery with a portico in the front. The sides of the stairways are decorated with interwoven feathered serpents. Pillars near this structure are in the form of the Toltec feathered serpent and human figures.
At the top is a square stone-lined vertical shaft in the floor which extends downwards to the base of the pyramid, where it opens up on a natural cavern. The cave is 36 feet (11 meter) deep and when it was excavated, bones from several human burials were identified along with grave goods and offerings of jade, shell, rock crystal and copper bells.