The Great Pyramid was used as the center of many ceremonies by the occupants of Uxmal.

Located in the southern portion of the city, it is located in an area that seems to mimic the main religious center surrounding the Pyramid of the Dwarf. As in the main Nunnary Quadrangle, there is a pyramid in proximity to a 4 part quadrangle, in this case, The Pigeon Quadrangle. And, as can be found at the top of the Dwarf's Pyramid, the Great Pyramid also has a huge Chaak mask in the upper temple.

http://www.isourcecom.com/maya/cities/uxmal/greatpyramid.htm