Limestone

Puerto Princesa Underground River, Karst Formation: Nature's Wonder

Until the discovery of an underground river in Mexico ’s Yucatan Peninsula in 2007, the 8.2-kilometer long Puerto Princesa Subterranean River was reputed to be the world’s longest underground river. The underground river arises approximately 2 kilometers south-west of Mount Saint Paul at an altitude of 100 meters. “The subterranean river is the park’s main calling card, and it passes through a mystical limestone cave before emptying into the South China Sea ,” UNESCO said.