The river then breaks through a sandstone mesa (the Marburger Rücken to the west and the Lahnberge to the east) into a valley which encompasses the entire territory of the city of Marburg and its suburbs. The valley begins after the river passes the Marburger Rücken near Niederweimar, where the Allna enters from the right. At the valley's southern end, the Zwesten Ohm enters from the Lahnberge. The right (western) side of the valley is again formed by the Gladenbacher Bergland, from which the Salzböde enters the Lahn. On the left rises the Lumda Plateau, from which the eponymous river Lumda flows into the Lahn near Lollar. Gradually the valley widens into the Gießen Basin.