The Mexican cenotes system is a chain of natural sinkholes, resulting from the collapse of limestone bedrock that exposes groundwater underneath. Especially associated with the Yucatán Peninsula of Mexico, cenotes were sometimes used by the ancient Maya for sacrificial offerings. The term derives from a word used by the low-land Yucatec Maya — ts’onot — to refer to any location with accessible groundwater. (Wikipedia)

Pics by Christian Bachmann.