he Ossuary is often called "The High Priest's Grave" because it contains an ossuary - a communal grave yard - beneath its foundations.
The building itself shows combined Toltec and Puuc characteristics, and is definitely reminiscent of el Castillo. The Ossuary includes a pyramid of about 9 meters high, with a length of 38 m at the base and four stairways on each side, a sanctuary in the center and a gallery with a portico in the front. The balustrades of the stairways are decorated with interlaced feathered serpents. Pillars associated with this building are in the form of the Toltec feathered serpent and human figures.
Every corner of the upper temple formerly was decorated by 4 Chac masks, lying on top of each other.
Between the first two pillars is a square, stone-lined, vertical shaft in the floor which extends downwards to the base of the pyramid, where it opens up into a natural cavern. The cave is 11 m deep, and when it was excavated, bones from several human burials were identified along with burial items and offerings of jade, shell, rock crystal and copper bells.
Several structures are aligned Between the Xtoloc temple and the Ossuary: the Platform of Venus (which is similar in design to the structure of the same name next to El Castillo), the Platform of the Tombs, and a small, round structure that is unnamed. These three structures were constructed in a row extending from the Ossuary. Beyond them the Ossuary platform terminates in a wall, opening up to a sacbe that runs more than hundred meters to the Xtoloc temple.