In 2002, remains of pile dwellings over 4,500 years old were discovered in the Ljubljana Marshes, now protected as a UNESCO World Heritage Site, along with the Ljubljana Marshes Wooden Wheel, the oldest wooden wheel in the world. It shows that wooden wheels appeared almost simultaneously in Mesopotamia and Europe. In the transition period between the Bronze Age to the Iron Age, the Urnfield culture flourished. Archaeological remains dating from the Hallstatt period have been found, particularly in southeastern Slovenia, among them a number of situlas in Novo Mesto, the "Town of Situlas". In the Iron Age, present-day Slovenia was inhabited by Illyrian and Celtic tribes until the 1st century BC.