Celtic tribes colonized Europe from the east. Around 500 B.C. they had reached Switzerland and eastern France. Their culture is known as the La Tène period (450 - 50 B.C.) of the Iron Age. This name comes from an excavation in western Switzerland (Lake of Neuchâtel). At this time, Switzerland's relatively flat midlands from Lake Geneva to Zurich were the territory of a celtic tribe named Helvetians.