The Pinnacles       The pinnacle formations of Gunung Api and Benarat are spectacular examples of this type of karst feature. The Pinnacles have been formed in tensional joints in the limestone bed at Mulu, which often occur at the edges of plateaux or valleys as pressure is released, as the rock above is eroded and the weight decreases. As the joints were formed, water percolating through the soil reacted in a process of dissolution to further shape and deepen the formations. The reason for the spectacular nature of the formations at Mulu lies in the consistent nature of its limestone beds and the even joints that were formed as a result and the high levels of rainfall that the area has experienced in geological time. Today the pinnacles tower above the surrounding landscape, some reaching heights of 40 to 50 metres. As water has continued to erode and dissolve the rock, the formations have taken on their razor-like appearance.