Wookey Hole Caves then passes through major cave systems such as Swildon's Hole, Eastwater Cavern and St Cuthbert's Swallet, around Priddy, but 95% is water that has percolated directly into the limestone. The southern slopes of the Mendip Hills largely follow the flanks of an anticline, a fold in the rock that is convex upwards and has its oldest beds at its core. On the Mendips the crest of the anticline is truncated by erosion, forming a plateau. The rock strata here dip 10–15 degrees to the southwest. The outer slopes are mainly of Carboniferous Limestone, with Devonian age Old Red Sandstone exposed
Udayagiri and Khandagiri Caves hill (Udayagiri). Marshall has counted more than 35 caves in both the hills, while M.M. Ganguli has enumerated only 27 caves. The number of existing caves at Udayagiri is 18, while Khandagiri has 15. The local names of the existing caves are listed below, numbered according to the enumeration of the Archaeological Survey of India. In Udayagiri, Hathigumpha (cave 14) and Ganeshagumpha (cave 10) are especially well known due to art treasures of their sculptures and reliefs as well as due to their historical importance. "Raninka Na'ara" (Queen's Palace cave, cave 1) is also an extensively carved cave and elaborately