Recognized as one of the New Seven Wonders of Nature, the Puerto Princesa Subterranean River is one of the longest navigable underground rivers in the world, flowing 8.2 kilometers through a spectacular limestone cave system before emptying directly into the South China Sea. Visitors board small paddle boats that glide silently through massive cathedral-like chambers adorned with dramatic stalactites, stalagmites, and rock formations shaped over 20 million years. The cave is home to a thriving ecosystem including nine species of bats that form swirling columns overhead, cave swiftlets, giant spiders, and unique invertebrates found nowhere else on Earth. The journey from Sabang beach to the cave entrance is itself spectacular — a 20-minute boat ride along a pristine coastline backed by towering karst cliffs draped in ancient forest, home to monitor lizards and long-tailed macaques.

Pro tip: Secure your permit through your hotel or a registered tour operator at least two days before your visit — walk-in permits are extremely limited and often sell out, especially during peak season.