West of the Matmata Hills, the terrain is dry country, the Jebel Dahar, and then impassable sand of the Grand Erg Oriental. The Oasis town of Gabès lies on the coast where the plain meets the route from the Tebaga Gap. North of Gabès, the road to Sfax, an ancient caravan route to Libya and points east, passes between the sea and the Chotts and this was Montgomery's only route north, a way blocked by the Mareth Line.