Located at about 70km northwest of the city, the Puerto Princesa Underground River features a limestone karst mountain landscape that inside spans a staggering 8.2km, making it widely known as the second-largest navigable underground river in the world and is also declared as one of the 7 Wonders of Nature and a UNESCO World Heritage Site in 1999. 

 

Being its scenic views of limestone formations, cavernous chambers, and wild animals, the northwest attracts tourists yearly, mainly to boat down the sunless Puerto Princesa Underground River.