Sahel is the Arabic word for "border." This seasonally dry West African region of steppes, thorny woodlands and savannas forms the borderline between the Sahara Desert and the tropical rain forests to the south. Our journey across the Sahel begins on Atlantic shores. In Senegal, it includes the infamous slave house on Goree Island and West Africa's largest National Park, the Niokolo-Koba on the river Gambia. We also visit Mali, the Niger Delta, Djenne, Mopti and the exotic Dogon Country of the Bandigara Escarpment.