The Palawan Underground River stretches 8.2 kilometers beneath a mountain and into the sea. Located in the Puerto Princesa Subterranean River National Park, this underground river is the longest navigable subterranean waterway in the world. In 2012, it was recognized as one of the New 7 Wonders of Nature, joining a list that includes the Amazon Rainforest and Ha Long Bay.
Boat tours take visitors through the first 4.3 kilometers of the river, gliding silently through cathedral-sized chambers where stalactites and stalagmites have been forming for millions of years. The formations take on shapes that guides have named over the decades: a giant mushroom, the Holy Family, a vegetable garden frozen in stone. Thousands of swiftlets nest in the cave ceiling, and the deeper chambers are home to monitor lizards, long-tailed macaques, and several species of bats.
The river flows directly into the South China Sea, making it one of the few underground rivers in the world with a direct ocean connection. The tidal influence reaches far into the cave system, creating a unique brackish water ecosystem that scientists are still studying.
If you have visited the Underground River, what was the most breathtaking formation you saw inside the cave?