Covering over 2.15 million square kilometers (830,000 square miles), including 2,640 km of coastline, the Kingdom is the largest country in the Middle East. The geography varies from rugged mountains with green valleys, to vast expanses of rolling sand dunes, to beautiful aquamarine waters next to sandy beaches. Although a few mountainous areas in the southwest can have torrential rain, most of the country experiences hot desert conditions with some humidity along the coasts. Dust storms also occur from time to time in the plains and coastal areas.