Cenote Ik Kil is one of the places I take my friends and family if they are here visiting in Mexico.
According to Wikipedia, “A cenote is a natural pit, or sinkhole, resulting from the collapse of limestone bedrock that exposes groundwater underneath."
Mayas still consider cenotes to be a sacred place. There are thousands of them on the Yucatan Peninsula, and there are different types: semi-open, underground and open.