Puerto Princesa Subterranean River National Park

"Puerto Princesa Underground River Puerto Princesa Underground River is set in a protected area of the St. Paul Mountain Range in Palawan. It’s a five-mile stretch of the Cabayugan River that runs through a huge limestone cave and directly into the West Philippine Sea near Sabang village (the bottom half of the river is tidal). Announced as one of the New7Wonders of Nature in 2012, it's hard to fully envision unless you experience it for yourself. Reservations are required for the tours, which enter the underground river on a small boat. The boatman manually paddles you in as the light fades, the water becomes pitch-black, and you almost lose sight of the person beside you. The boatman will then start flashing his tiny light on the stalactites, stalagmites, and other rock formations you pass. The tour takes about 45 minutes and covers only a mile or so of the river (the inner portion is closed to the public)."