The limestones belong to the Melinau Limestone Formation and are estimated to be 4000 to 5000m thick. In the south-east of Mulu Park sandstones are dominant. The hightest relief in the region (Gunung Mulu) is located in these sandstones. Mulu's landforms are outstanding examples of erosional processes on both of these rock types (limestones and sandstones). Among the most remarkable karst features are the world's finest example of a karst collapse (The Garden of Eden) and the sharp pointed bladed limestone Pinnacles, some of which are 45m high on the northern end of Gunung Api. There are also numerous examples of cone karst and tower karst. Another interesting feature of the landscape is the drainage through deeply incised gorges (Sungai Melinau at Melinau Gorge and Sungai Medalam to the north) in the limestones.