Cenote Zaci (Valladolid, Mexico)

From Wikipedia: "A cenote (Spanish: [seˈnote] or[θeˈnote]; plural: cenotes; from Yucatec Maya dzonot orts'onot, "well") is a deep natural pit, or sinkhole, characteristic of Mexico, resulting from the collapse of limestone bedrock that exposes groundwater underneath. Especially associated with the Yucatán Peninsula, and some nearby Caribbean islands, cenotes were sometimes used by the ancient Maya for sacrificial offerings."