Easily the best thing we did in Puerto Princesa was a silent ride through an underground river. Moving through pitch black caverns by flashlight, we listened to a tour guide on individual headsets as to not disturb the animals. Thousands of swirling bats were an constant reminder to keep mouths closed as we gaped in wonder (we hear bat poo tastes even worse than it smells). Each section has a different name based on what the rock formations look like, for example, The Cathedral opens up with rocks formations shaped like religious figures including the Virgin Mary, and The Market has formations that look like fruits and vegetables. It is easy to see why it is one of the New 7 Wonders of Nature.