The Nunnery Annex is located immediately adjacent to the Nunnery and while it is from the early Maya period of Chichén Itzá, it shows some influence of later residence. This building is of the Chenes style, which is a local Yucatan style. It has a lattice motif on the roof comb, complete with Chac masks, but it also includes an undulating serpent running along its cornice. The decoration begins at the base and goes up to the cornice, with the façade completely covered with several rain god masks with a central richly clad human figure over the doorway. A hieroglyphic inscription is on the lintel.
But the best thing about the Nunnery Annex is that, from a distance, the whole building is a chac mask, with the human figure as the nose and the doorway the mouth of the mask.