Puerto Princesa Subterranean River

In 1898, the American Zoologist Dean C. Worcester described mysteries and wonders of the Philippine Islands from his travels, including the tantalizing reference, “If accounts are to be believed, of a lake opening to the sea by a subterranean river.”

This extraordinary river does indeed exist, snaking over five miles underground through limestone caves, linking lake to ocean in the Palawan province of the Philippines. 

One of the world's longest underground waterways, the Cabayugan River passes though 15 miles of caves, studded with stalactites and stalagmites, the water rising and falling with the tides of the South China Sea at its end. The caves have been a National Park since 1971, made a UNESCO World Heritage Site in 1999, and was named one of the "New Seven Wonders of Nature" in 2012.