Mabinay

Due to bat guano and urine.

2,222m long.

Nice gardens with plenty of shade trees have three pavilions where you can leave your bags and gear and use clean toilets. The cave is about 150m walk over rough karst and through sheltering trees. Since the cave atmosphere has pretty well 100% humidity you might want to pause for a few moments to cool off before you enter. There is an iron walkway at relatively high level of about 140m from the cave entrance and artificial lighting. The formations are interesting and extremely varied, but of a uniform whiteness except where they have been contaminated. Many will be interested to see the rhinoceros bats hanging from the ceiling, but watch where you place your hands because of guano deposits. The air is not foetid or unpleasant despite the lack of any air currents. For many the highlight may well be the opportunity to get very close to tiny Balinsasayaw swifts nesting in the ceiling about 1m above your head. (The caves have to be kept locked to prevent the theft of their valuable nests that are prized for making birds' nest soup. The nests built, with the birds saliva, have high levels of calcium, iron, potassium, and magnesium and can fetch about ₱40 per gram. According to traditional Chinese science, these soups are believed to help maintain skin tone, balance qi {"life energy"}, help digestion, alleviate asthma, boost the libido and reinforce the immune system.)

Large colonies of three different species of bat and an opening that allows a shaft of sunlight to penetrate.

At a length of some 8,870m, this cave system is the second longest in the Philippines after St Paul's Underground River in Palawan's National Park. It's not a cave for casual visitors since it can only be accessed by swimming 20m across an underground torrent of by rappelling down from a squeeze in the roof. Seasoned spelunkers will be rewarded with large galleries, narrow corridors, and some pretty extreme water challenges.

Contains the "Berlin Wall".

The most accessible of them all.