Geography of Bahrain  The Kingdom of Bahrain consists of Bahrain Island and 33 of the 37 Bahrain Islands, lying in the Persian Gulf's Gulf of Bahrain off the north shore of Asia's Arabian Peninsula. Bahrain's capital city is Manama. The islands are about off the east coast of Saudi Arabia and from Qatar. The total area of the country is about , about 3.5 times the size of the District of Columbia. Bahrain Island accounts for about 78% of the kingdom's land area, comprising . It is long from north to south and at its widest point stretches from east to west. The island is surrounded by several of the Middle East's large petroleum fields and commands a strategic position amid the Persian Gulf's shipping lanes. Following the return of Janan to Qatar in March 2001, that state of Bahrain consists of 33 natural islands in the archipelago. Around most of Bahrain is 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 – chiefly thorn trees and scrub. There is a fertile strip five kilometers wide along the northern coast on which date, almond, fig, and pomegranate trees grow. The interior contains an escarpment that rises to 134 meters, the highest point on the island, to form Jabal al Dukhan (Mountain of Smoke), named for the mists that often wreathe the summit. Most of the country's oil wells are situated in the vicinity of Jabal al Dukhan. One author writes about the geology of the nation: "Bahrein lies on a portion of the ancient Tethys Ocean geosynclinal belt represented today by the Persian Gulf. The formation of the principal island is the result of pressure from the mountain masses of Persia against the crystalline platform of central Asia, the thrust being absorbed by gentle folding in the geosynclines. The structure of Bahrein is that of a large, single, closed dome covering the entire faulting". Rocks exposed at the surface consist of:   In addition to Bahrain Island, other islands of significance include Nabih Saleh, which is northwest of Sitrah; Jidda Island and Umm as Sabaan, to the north of Umm an Nasan; and a group of islands, the largest of which is Hawar, near the coast of Qatar.