Cenoté
"East of the major Chichén Itzá ruins is a dark underground world the Mayans called Cenoté. They are deep water filled sinkholes formed by water percolating through the soft limestone above. Since the porous soil held little water, these underground bodies were extremely important to the city. A visit to one is a spine chilling experience. Entry is through a vertical hole with narrow stair steps carved by the Mayan's themselves. The air is thick and musty. One misstep on the slimy ledges threatens to send you falling over 20 feet."
Visit the dark underground world of a Cenoté