Reachable only via a short boat trip, the entrance of the subterranean river cavern lies close to the coastline north of Puerta Princessa. The cave itself is stunning, with enormous stone formations and caverns deep in the mountain. The river is navigable by canoes, in which small groups are guided through the caverns. The total absence of light gives the tour a bit of a spooky atmosphere. Having seen some large caves, this is definitely one of the more interesting and astonishing ones. If you get the chance, go and visit!

What actually is a downside of the trip are the masses of tourists visiting the site, some of which show little or no respect to this natural wonder. While guides ask you to remain silent and under no circumstances touch the rock formations some individuals ignore such requests entirely, ruining the experience for others and - even worse - in some cases damaging the site. In my opinion, the amount of tourists per day should be strictly regulated.