Undoubtedly, one of the most beautiful and truly unique phenomena in Yucatan are cenotes. A multitude of these fresh water sinkholes can be found throughout the area exposed as a result of limestone cave roof collapse. To the ancient Maya cenotes were sacred points of entrance to Xibalba, the underworld inhabited by death gods and spirits whose stories are told in Mayan creation myth of Popol Vuh. In reality cenotes are a small glimpse into an entire underground river system covering most of Yucatan Peninsula, which actually looks like an enormous subterranean Swiss cheese. What’s even more incredible is that all these caves were originally created by a meteorite impact 65 million years ago, same one that caused mass extinction of the dinosaurs. Scientists actually used the increased density and circular alignment of cenotes to identify the rim of Chicxulub crater, which is more than 180 km (110 mi) in diameter and is one of the largest confirmed impact structures on Earth! These are all the things I think about as I jump in a cenote on a particularly hot afternoon.