In the north and northwest, the Swiss Plateau is sharply delimited geographically and geologically by the Jura Mountains. In the south, there is no clear border with the Alps. Usually, the rising of the terrain to altitudes above 1500 metres AMSL (lime Alps, partly sub-alpine molasse), which is very abrupt in certain places, is taken as a criterion for delimitation. Occasionally the regions of the higher Swiss Plateau, especially the hills of the canton of Fribourg, the Napf region, the Töss region, the (lower) Toggenburg, and parts of the Appenzell region are considered to form the Swiss Alpine foreland in a narrow sense. However, if a division into the three main regions Jura Mountains, Swiss Plateau and Alps is considered, the Alpine foreland belongs clearly to the Swiss Plateau. In the southwest, the Swiss Plateau is confined by Lake Geneva, in the northeast, by Lake Constance and the Rhine.