The area known as Croatia today was inhabited throughout the prehistoric period. Fossils of Neanderthals dating to the middle Palaeolithic period have been unearthed in northern Croatia, with the most famous and the best presented site in Krapina. Remnants of several Neolithic and Chalcolithic cultures were found in all regions of the country. The largest proportion of the sites is in the river valleys of northern Croatia, and the most significant cultures whose presence was discovered include Baden, Starčevo, and Vučedol cultures. The Iron Age left traces of the early Illyrian Hallstatt culture and the Celtic La Tène culture.