Between these two mountain systems lies the Swiss Plateau, or Mittelland, a basin that stretches across much of central Switzerland. It extends from Lake Geneva (Lac Leman) in the far southwest to the Bodensee (Lake of Constance) in the far northeast. A region about 50 km (30 mi) wide with an average elevation of about 400 m (about 1,300 ft) above sea level, the plateau consists of gently-to-moderately rolling terrain punctuated by hills. Most of Switzerland’s large towns and about three-quarters of the Swiss population are located in this region. The plateau contains many lakes and rivers, as well as Switzerland’s most fertile soils.