Most of the island of Bahrain is in a relatively shallow inlet of the Persian Gulf known as the Gulf of Bahrain. The seabed adjacent to Bahrain is rocky and, mainly off the northern part of the island, covered by extensive coral reefs. Most of the island is low-lying and barren desert. Outcroppings of limestone form low rolling hills, stubby cliffs, and shallow ravines. The limestone is covered by various densities of saline sand, capable of supporting only the hardiest desert vegetation such as chiefly thorn trees and scrubs. A wide fertile strip of land exists along the northern coast on which date, almond, fig, and pomegranate trees grow. The interior contains an escarpment that rises to , the highest point on the island, to form the Mountain of Smoke, named as such due to the mists that often wreathe the summit. Most of the country's oil wells are situated in the vicinity of the mountain.