The Puuc style of architecture consisted of veneer stones cemented in place over a rubble core, stone roofs with corbeled vaulting and intricately detailed facades in geometric and mosaic stone veneers. The smaller structures like this one have plain plastered lower elements combined with an intricate roof comb--that's the free-standing tiara on the top of the building, in this case with a lattice crust mosaic. The roof design in this structure has two Chac masks looking out; Chac is the name of the Mayan Rain God, one of the dedicatory gods of Chichén Itzá.
Falken adds: What used to be called Chac masks are now thought to be "witz" or mountain deities that inhabit mountains, especially those at the midpoints of the cosmic square. Thus these masks bestow a quality of "mountain" to the building.