Palawan - St. Paul Subterranean National Park (Underground River) Located in Sabang, Puerto Princesa City, Palawan, Philippines To reach Sabang it takes 2-3 hours land trip from downtown Puerto Princesa City. Sabang is still in Puerto Princesa City, the largest city in the Philippines. aside from the boat ride, another way to reach the underground river is the monkey trail It is believed to be one of the longest navigable underground river in the world which features cathedral-like caverns and domes. The stalactites and stalagmites resembles like religious images, fruits, and birds. The land form in the park are associated with rocky mountains of marbles and limestones.