Switzerland in the Roman era after which the area began to be occupied by Germanic peoples. The Swiss plateau, within the natural borders of the Alps to the South and East, Lake Geneva and the Rhône to the west and the Rhine to the north, was recognized as a contiguous territory by Julius Caesar. This area had been dominated by the La Tène culture since the 5th century BC, settled by a mostly Celtic population (Gauls), of which the Helvetii were the most numerous, but which also included the Rauraci in north-west Switzerland centered on Basel, and the Allobroges around Geneva. South of the Swiss
Swiss Plateau the southwest, the Swiss Plateau is confined by Lake Geneva, in the northeast, by Lake Constance and the Rhine. Geologically, the Swiss Plateau is part of a larger basin that extends beyond the border of Switzerland. At its southwestern end, in France, the plateau, in the Genevois, ends at Chambéry where Jura and Alps meet. At the other side of the Lake Constance, the plateau continues in the German and Austrian Pre-Alps. Within Switzerland, the Swiss Plateau has a length of about , and its width increases from the west to the east: In the Geneva region, it is about