Planning of underground space is extremely important for land-squeezed Singapore. Like surface planning, the planning for underground space should also incorporate economic, social and environmental considerations. Underground space can be used more effectively if the various functions such as transportation, communication, etc., are coordinated. Subsurface development should also be considered together with surface development plans, since surface development could affect the optimized use of the underground space in the Bukit Timah granite. Site selection is the most crucial factor in the planning stage of a cavern project. It must take into consideration geologic, hydrologic, environmental, psychological, surface development, social, economic, and political factors. A computerized tool that is founded on a Geographical Information System (GIS) platform is needed to collect and analyse all of the factors that govern the selection of a cavern site.