Palawan's Underground River
The Puerto Princesa Subterranean River National Park is located about 50 kilometres (30 mi) nort...
In 2010, a group of environmentalists and geologists discovered that the underground river has a second floor, which means that there are small waterfalls inside the cave. They also found a huge cave dome, measuring 300 meters above the underground river, incredible rock formations, large bats, a deep water hole in the river, more river channels, another deep cave, marine creatures, and more. And because it's very dark inside and very hard to get oxygen, it's dangerous for humans, so they didn't uncover all of the mysteries of this deep underground river.