From http://www.lonelyplanet.com/mexico... Mexico’s Yucatán Peninsula has undeniably stunning beaches around Cancún, Playa Del Carmen and Tulum. But those who wish to cool off from the sun and teeny-bikini flashiness can escape to a secret underworld of turquoise pools where Mayans communicated with the gods. At these hidden locations, you can swim in crisp mineral-rich waters in magical caves or under a jungle-framed sky and feel lost in another time. Cenotes are natural swimming holes formed by the collapse of porous limestone bedrock, which has revealed a secret subterranean world of groundwater pools. Most cave cenotes have fresh water that has been meticulously filtered by the earth, making them so clear and pure that you can see straight through to small fish frolicking in the plant life below. Open-air cenotes also have clear water, and often are home to vitamin- and mineral-rich algae that nourish and protect your skin. Underwater photographers will be thrilled with the clear waters, which allow for aquatic-playground shots in high-definition clarity. The Mayans revered cenotes because they were a water source in dry times; the name cenote means 'sacred well'. Mayans settled villages around these spiritual wells and believed that they were a portal to speak with the gods. Today you can still see why cenotes held the Mayans in awe. Swimming in the pristine waters feels like stepping into prehistory, where giant tropical trees and vines form wild cathedral walls leading up to shafts of sunlight. Read more: http://www.lonelyplanet.com/mexico... - Son of Groucho