They went looking for a sacred well. But archaeologists working beneath the ancient Mexican city of Chichén Itzá discovered something far more surprising: vases, decorative plates, incense burners, and other ritual artifacts left more than 1,000 years ago in an extensive cave system. For the ancient Maya, caves were sacred spaces, considered doors to the underworld. Excavation of the site will offer important clues about Maya civilization and the history of Chichén Itzá. The decline of the great city in the thirteenth century is still something of a mystery.