The Puerto Princesa Subterranean is one of the most important protected areas of the Philippines. It features a spectacular limestone or karst landscape withone of the most complex cave systems. It contains an 8.2 km long underground river that flow directly to the sea. formations, and a 20 million year old Miocene age serenia fossil in the cave further add to its scientific value. The Puerto Princesa Underground River is declared as one of the New 7 Wonders of Nature.