If you keep walking east from El Castillo and the Hall of the Frescoes, you will encounter a series of buildings with columned halls and, at the center, the so-called Observatorio or Observatory.
This is a circular building, probably with a ceremonial purpose. It has an internal hallway and its walls were covered with stucco and painted. This building is similar to the building of the same name at Chichén Itzá. Evid3nce supporting its use as an astronomical observatory includes a stone with a carving illustrating the position of Venus.