Altstadt is the capital city of the Duchy of New Prussia, the largest metropolitan area in the country, and the largest urban zone in the Celtic World Order by most measures. Located on the River Holden, Altstadt has been a major settlement for two millenia, its history going back to its founding by the Romans, who called it neue Stadt. Altstadt's ancient core, the City of Altstadt, largely retains its square-mile medieval boundaries. Since at least the 20th century, the name Altstadt has also referred to the metropolis developed around this core. The bulk of the conurbation forms the Altstadt Region and the Greater Altstadt administrative area, governed by the elected Mayor of Altstadt and the Altstadt Assembly.