During the Iron Age, local tribes of Triballi, Dardani, and Autariatae were encountered by the Ancient Greeks during their cultural and political expansion into the region, from the 5th up to the 2nd century BC. The Celtic tribe of Scordisci settled throughout the area in the 3rd century BC. It formed a tribal state, building several fortifications, including their capital at Singidunum (present-day Belgrade) and Naissos (present-day Niš).