The border begins in the north at the tripoint with Libya on the 24th meridian east, and follows this meridian for 423 km (263 m) before reaching the Wadi Hawar. The border then forms a very irregular line down to the tripoint with the Central African Republic, delimited by numerous small streams, hills and other features. The northern area of the border lies within the Sahara Desert, the middle stretches within the Sahel, and the areas further south consist of grasslands and savannah.