World's Strangest Natural Wonders
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Puerto Princesa Subterranean River, Philippines
The five-mile-long Puerto Princesa Subterranean River on the island of Palawan is the world’s longest navigable underground river. It flows to the South China Sea through a nearly 15-mile-long cave that’s lined with stalactites and stalagmites and contains the largest cave chamber in the world. The surrounding park is a UNESCO World Heritage Site that’s equally impressive and is home to more than 800 plant species, 165 kinds of birds, 30 mammal species, 19 varieties of reptiles, and nine different species of bats.