Gunung Sewu UNESCO Global Geopark is a classic tropical karst landscape in the south central part of Java Island well-known in the world, and dominated by limestone. The limestone is of Neogene age and consists of calcareous-tuffaceous clastic facies (Oyo and Kepek formations) as well as reef facies (Wonosari formation). Late Oligocene to Early Miocene rocks of volcanic-origin clastic, volcanic and marine sediments underlie these limestones. Quaternary river and lake deposits represent the youngest units. There is still tectonic activity in the region because Gunung Sewu is located in front of an active subduction zone between the Indian Ocean, Australian and Eurasian plates. Active uplifting is taking place since 1.8 million years and produces very visible river terraces at Sadeng dry-valley as well as coastal terraces along the southern coast of the UNESCO Global Geopark.