While in Mexico, I'm hoping to do some traveling around to various historic sites. The Yucatan peninsula is filled with ruins and temples of the Maya civilization. When I lived near Mexico City I visited some Aztec/Toltec/Olmec ruins, but I've never been to this area of Mexico before, so I'm looking foward to it. The Wikipedia link above has a ton of information about the Maya, including this section about their Pyramids and temples. Between visiting such sites, some colonial cities, hanging on the beach, and sleeping, it should be a pretty busy visit.