In the west, it is bounded by the shores of the Atlantic Ocean. From northeast to southwest, Morocco, Western Sahara (mostly unilaterally annexed by Morocco), and Mauritania make up the roughly 2,000 kilometers of Arab Atlantic coastline. The southwestern sweep of the coast is gentle but substantial, such that Mauritania's capital, Nouakchott (18°N, 16°W), is far enough west to share longitude with Iceland (13–22°W). Nouakchott is the westernmost capital of the Arab World and the third-westernmost in Africa, and sits on the Atlantic fringe of the southwestern Sahara. Next south along the coast from Mauritania is Senegal, whose abrupt border belies the gradient in culture from Arab to indigenous African that historically characterizes this part of West Africa.