Kilim Geoforest Park was developed on the oldest limestone of the country i.e. the Setul Formation. It is endowed with numerous geosites where highly significant geological features such as caves, fossils, geological age and formation boundaries, rock types, geological structures, and beautiful landform can be observed.
Kilim Geoforest Park features breathtaking landscape of nearly vertical karstic hills with pinnacles of various shapes and sizes. Perhaps among the main factors contributing to the formation of such beautiful karstic landscape are its generally thin beds and flat to very gently dipping attitude with many high angle and vertical faults and fractures as well as its better exposure to the open sea.
Many caves with beautiful cave deposits and features were developed within this park including the famous Kelawar Cave. A fresh water doline-lake was developed at Langgun Island. Several fossil horizons are also discovered at Langgun Island with different fossils that thrived in different palaeo environment.