Imagine paddling through a massive limestone cave where a crystal-clear river flows directly into the sea deep inside a mountain. The Puerto Princesa Subterranean River (also known as the Puerto Princesa Underground River) in Palawan, Philippines, is exactly that: the world’s longest navigable underground river and one of the New 7 Wonders of Nature.
What Makes It Unique?
This subterranean river runs 8.2 kilometers (5.1 miles) entirely underground through a spectacular karst limestone cave system before emerging into the South China Sea. Tourists can explore the first 4.3 km by boat, making it the longest navigable underground river globally.
- Direct sea connection: Brackish water near the entrance (mix of fresh river and saltwater).
- Stunning formations: Towering stalactites, stalagmites, and vast chambers resembling cathedrals.
Location and Geology
Located in Puerto Princesa Subterranean River National Park on Palawan Island, the cave formed over millions of years as rainwater dissolved limestone, creating vast chambers. The mountain above (St. Paul Mountain) hides this hidden waterway.
Biodiversity and Ecosystem
The park is a UNESCO World Heritage Site for its outstanding biodiversity:
- Over 800 plant species.
- Unique cave fauna: Bats (millions roost inside), swiftlets, crabs, and fish adapted to darkness.
- Marine life near the entrance: Monitor lizards, monkeys, and sea eagles in the surrounding mangrove forest.
The cave’s “guano” (bat droppings) supports a rich underground food web.
Visiting the Underground River in 2025
Tours remain highly regulated to protect the site:
- Standard tour: Paddle boat with audio guide (no talking allowed inside to minimize disturbance).
- Duration: About 45 minutes inside the cave.
- Access: From Puerto Princesa City (2-hour van ride to Sabang, then short boat to entrance).
- Tips: Book permits in advance; limited daily visitors. Best in dry season (December–May).
It’s a bucket-list experience blending adventure, geology, and nature.
This natural marvel showcases Earth’s hidden wonders beneath our feet.
