Mayan Cenote (from Dzit Nup meaning Mouth of the Underworld)

http://ngm.nationalgeographic.com/2013/08/sacred-cenotes/nicklen-schwarz-photography?source=hp_dl2_ngm_sacred_cenotes_20130720?source=email_inside&utm_source=NatGeocom&utm_medium=Email&utm_content=inside_20130725&utm_campaign=Content