The Sahel runs 3,862 km from the Atlantic Ocean coast of Mauritania in the west to the Red Sea coast of Sudan in the east. The ecoregion definition takes in part of other countries but for the purposes of this travel guide, it includes all of Chad, Mali, Mauritania, Niger and Sudan. The region consists of semi-arid grasslands, savannas, steppes, and thorn shrublands lying between the Central African wooded savanna to the south, and the Sahara to the north.
The topography of the Sahel is mainly flat, and the region mostly lies between 200 and 400 meters elevation.
Over the history of Africa the region has been home to some of the most advanced kingdoms benefiting from trade across the desert. Collectively these states are known as the Sahelian kingdoms which were a series of empires, based in the Sahel, which had many similarities. The wealth of the states came from controlling the Trans-Saharan trade routes across the desert. Their power came from having large pack animals like camels and horses that were fast enough to keep a large empire under central control and were also useful in battle. The first large Sahelian kingdoms emerged after 750, and supported several large trading cities in the Niger Bend region, including Timbuktu, Gao, and Djenné.
Annual rainfall varies from around 200 mm in the north of the Sahel to around 600 mm in the south.