The State of Qatar occupies a long, narrow peninsula jutting into the Persian Gulf. The peninsula is about 200km [12mi] long, with a greatest width of 90km [56mi]. The land is mostly flat desert covered by gravel and loose, wind-blown sand. Sand dunes occur in the SE. There are also some barren salt flats. The highest point, on a central limestone plateau, is only 98m [321ft] above sea level. Qatar also includes several offshore islands and coral reefs. Fresh water is scarce and much of the water supply comes from desalination plants.