Which Philippine underground river is a UNESCO World Heritage site?

The Philippine underground river recognized as a UNESCO World Heritage site is the Puerto Princesa Subterranean River.

The river flows through Puerto Princesa Subterranean River National Park on Palawan Island. It travels through a limestone karst cave before reaching the South China Sea, creating a rare landscape where an underground waterway runs directly into a marine environment.

The protected river is about 8.2 kilometers long, although tourist boat trips cover only a shorter section of the cave. Visitors encounter stalactites, stalagmites, chambers, and cave-adapted wildlife while traveling beneath the forested karst mountains. Tidal influence also reaches into parts of the underground system.

The site was inscribed as a UNESCO World Heritage property in 1999 for its exceptional natural scenery, biodiversity, and geological significance. It is sometimes confused with other Philippine attractions such as Sohoton Cove or Hinatuan Enchanted River, but neither is the UNESCO underground-river landmark described here.