The Southern Mountains are less lofty and more rounded than their eastern and northern counterparts, never exceeding 2,000 metres (6560 feet) in height. Their shape has been compared to that of a westward travelling looper caterpillar (inchworm). The Fachnar Hills, to the west, are isolated from the main mass by rivers flowing north into Delisle Bay or south into Fachnar Bay. Along the south coast are a series of bays, into which rivers empty from the north; the largest inlet is the huge Arcturus Bay. From their eastern ridges, several other small rivers flow eastward into the sea. In addition, there is a basin of inland drainage near the middle of the Southern Mountains, centering upon Lake Vanadha, Rockall’s largest lake.