Bukilat Cave is a large natural cavern in the southeastern part of the island. Because of naturally formed piercings in its canopy, the interior is well illuminated. There are many stalactites and stalagmites.
The cave served as shelter for the people living in the island from the Japanese invaders during World War II. Hidden treasures are rumoured to be scattered throughout the area.
There are several other less popular caves on Poro island.
Buho Rock is a hole in a cliff wall said to have been formed when a Spanish warship mistook it for an enemy ship in the mist and fired cannon into it. It is reached by a stone staircase, and offers views of Poro and the sea.