Subterranean River

Set among the lush nature of Palawan’s Puerto Princesa Subterranean River National Park (look out for monkeys in the canopy and monitor lizards in the undergrowth as you pass through), the Puerto Princesa Subterranean River is the longest navigable underground river in the world. Stretching 15 miles under the dramatic limestone karst crags of the St Paul Mountain Range, it flows into the South China Sea, its route an intricate network of tunnels and chambers carved over millions of years.

A UNESCO World Heritage Site and one of the New 7 Wonders of Nature, you can explore the river by boat, a 45-minute ride that takes you 2.5 miles into the tunnel. As you float through the peaceful darkness, the only sounds the clicking of bats and drip drip of water, you’ll learn all about the geology and ecology of this underground world while spotting dramatic stalactites and stalagmites and passing through cathedral-like caverns.