Osijek is the fourth largest city in Croatia. It is the largest city and the economic and cultural centre of the eastern Croatian region of Slavonia, as well as the administrative centre of Osijek-Baranja County. Osijek is located on the right bank of the river Drava, 25 kilometres upstream of its confluence with the Danube. Osijek is a city stepped in history; it was once a major Habsburg military base. Refined architecture typifies the main streets of its Upper Town while the former Tvrđa fortress now houses bars, restaurants and a regional museum.