Puerto Princesa Subterranean River National Park or the underground river is one of the most or a must visit place among the World Heritage Sites of the Philippines. Its natural 8.2 km navigable underground river is believed to be the world’s longest underground river. The river can be found beneath a beautiful limestone karst mountain called St. Paul which was named after one of its peaks that resembles the dome of St. Paul Cathedral in Italy.
It is one of the centers of biodiversity conservation in Puerto Princesa, Palawan wherein different types of animal species can be seen on the mouth of the cave. You can see monkeys and large monitor lizards greeting you on your way to the mouth of the cave.