Kelawar Cave or Bats' Cave is located in the heart of Kilim mangrove swamps within the Kisap Forest Reserve. The cave is about 60 m long and was named as such because it supports hundreds of bats. It consists of two caves. The western cave has a floor area of about 270 m sq with a low roof (1-3m) trending northeast. The second cave is bigger, having a floor area of about 750m sq, with roof reaching 10m high and trending north-northwest.
Interesting features and structures in these caves include stalactites, stalagmites, and fallen rock blocks. The most interesting and important features is the occurence of old shells encrusting on the cave wall and roof. Radiocarbon dating indicated that the shells are about 5000 years old. The altitude of the shells clusters shows that the sea-level at that time was 2 m higher than the present level.