How often do you get the chance to wander below the earth? These caves—the Mayan name of which translates as either "throne of the jaguar caves" or "caves of the hidden throne"—are dank and sometimes slippery slopes into an amazing rocky underworld. They are lighted to best show off their lumpy limestone stalactites and niche-like side caves. It's a privilege also to view in situ vases, jars, and incense burners once used in sacred rituals. These were discovered in the 1950s, and left right as they were. An arrangement of tiny metates (stone mortars for grinding corn) is particularly moving. At the end of the line is the underground cenote where Maya priests worshipped Chaac, the rain god. A sound-and-light show recounts Mayan history. From Chichén Itzá, you can catch a bus or taxi or arrange a tour at the Mayaland hotel. Although there's a six-person minimum, the ticket vendor will often allow even a pair of visitors to take the tour. Wear comfortable, nonslip walking shoes, and be brutally honest with yourself about your capabilities before venturing in. Do not attempt if you're claustrophobic or have heart or respiratory problems—the climb is steep, and the caves are hot and humid.