The country can be divided into four main areas from the south to the north. The low-lying, sandy, coastal plain which has a highest elevation of is, at most, wide. It is marshy and dotted with lakes and lagoons connected to the ocean. The plateaus of southern Benin, with an altitude ranging between , are split by valleys running north to south along the Couffo, Zou, and Oueme Rivers, an area that has been categorised by the World Wildlife Fund as part of the Guinean forest-savanna mosaic ecoregion. Then an area of flat lands dotted with rocky hills whose altitude seldom reaches extends around Nikki and Savé. Finally, the Atacora mountain range extends along the northwest border and into Togo with the highest point, Mont Sokbaro, at .