Also known as The High Priest Temple, The Ossuary is a pyramid at Chichen Itza with nine stepped blocks and a staircase on each side. Stairs count with balustrades carved with interlocking snakes that lead to a temple at the top, which entrance displays two snake columns.
It was built above a deep extense cavern, to which one can descend-to from the entrance made in the floor of the upper temple. At the entrance to the cavern, there are seven tombs which contained jade, rock crystal, shell and copper offerings.
It was designed for the sun register. Its orientation, at 17 degrees from north, allows one to observe a relevant astronomic event on the agricultural ritual calendar: the cenital pass of the sun from may 23rd to june 19th. The first date, on this latitude, matches with the beginning of the rainy season. It’s composed by a vertical air intake, where sun descends, initiating on the floor of the upper temple. Ending then, in the "Mother Rock", 10 meters deep, where several objects were found, such as medium-sized sculptures, bones and shell-made objects.
In practice, this cenital observatory is similar to other buildings found at Xochicalco, Morelos, Teotihuacan, Oaxaca and other locations. It was built, same as the others, in order to have more precise reference in time register. In terms of rituals, The Ossuary was made as a replic of the Cosmic Mountain, where sacred forces are manifested. On this structure, the creation of the cosmos by Gods in the Mythical Time is replicated. The sun penetrates trhough the air intake and fertilizes soil.
The Ossuary is one of the most complex buildings on site. It is known to be built over a deep cave. It is possible that this cave was considered a door to the underworld. Its architecture is very similar to the Pyramid of Kukulkan, with 4 staircases and an upper temple.
The most remarkable aspect of the Ossuary is its bust decoration. Full of different bas-relief snakes, birdmen, men with god-like masks and other representations. It also holds 894 AC’s incriptures.
On the upper foundation, 8 interlocked snakes decorate the edge of the structure. Four of the snakes are covered with turquoise disc and the other four with earrings. The three panels on the upper foundation are covered by bird representations. In total, there are 48 panels with fruit, cocoa beans, jewels and animal bas-relief.Source: Vela, Enrique, "El Osario", Arqueología Mexicana, edición especial núm. 27, pp. 64-65.