These caverns are the largest, most interesting cave system on the Yucatán Peninsula, and a treasure trove of data for archaeologists. Carbon dating of artifacts found here reveals that humans used the caves 2200 years ago. Chest-high murals of hands, faces, animals and geometric motifs were apparent as recently as 20 years ago, but so many people have touched them that barely a trace remains. Now, visitors to the illuminated caves see mostly natural limestone formations, some of which are quite lovely.