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
Geography of the Alps passes to the south of the Jura range before reaching Lake Geneva. An area of flat ground reaches from there to Lake Neuchâtel, continuing the border, with the Jura to the north-west and the Alps to the south east. From Lake Neuchâtel to its confluence with the Rhine, the Aare forms the border. The Black Forest is separated from the Alps by the Rhine and Lake Constance, but exact delimitation is difficult in southern Germany, where the land gently slopes up to meet the mountains (known in German as the "Schwäbisch-Bayerisches Alpenvorland", the "Swabian-Bavarian pre-Alps"). In Austria, the Danube runs