Almost 1h of Sumatra is continuous swamp extending some 1370 km down the whole east coast. There's an unbroken mountain wall ranging in altitude from 1575 m to 3700 m stretching along the entire west coast, Bukit Barisan (Parada of Mountains), including 93 volcanic peaks, 12 of them still active. On the western side of this range mountains plunge right into the sea. There's a chain of islands off the west coast, most with rocky reef-enclosed coasts, where the old ladang system of cultivation of taros and yams is still practiced. Most of the inhabitants on these islands of Nias, Mentawai and Enggano have been bypassed by the mainstreams of the 20th Century.