Palawan's St. Paul's underground river is said to be the world's longest underground river. The navigable part of the river inside the cave of the 4000-acre St. Paul Subterranean River stretches 8.2 kilometers in length (5 miles). However, this title is being disputed in Vietnam where an underground river known as Son Trach River reportedly extends 7 miles in length. Filipino explorers, however, claimed that once fully measured, St. Paul total length would reach 15 kilometers.
St. Paul Underground River in Palawan
