to contend with the temporal power of the Church, and after the Thirty Years War with Sweden, the masters of the surrounding Duchy of Bremen-Verden. In the late nineteenth century, Bremen was drawn by Prussia into the German Empire. With its new sea anchorage and wharves at Bremerhaven, it was the principal port of embarkation for German and central European emigrants to the Americas, and an entrepôt for Germany's late developing colonial trade. The Norddeutscher Lloyd (NDL), founded in Bremen in 1857, became one of the world's leading shipping companies. In the twentieth century, Bremen, a broadly liberal and social-democratic city, lost its autonomy under the Hitler regime. After World War Two, in which almost two thirds of the city's fabric was destroyed, this was restored. Bremen became one of the founding Bundesländer (or states) of the German Federal Republic. Geography Bremen lies on both sides of the River Weser, about upstream of its estuary on the North Sea and its transition to the Outer Weser by Bremerhaven. Opposite Bremen's Altstadt is the point where the "Middle Weser" becomes the "Lower Weser" and, from the area of Bremen's port, the river has been made navigable to ocean-going vessels. The region on the left bank of the Lower Weser, through which the Ochtum flows, is the Weser Marshes, the landscape on its right bank is part of the Elbe-Weser Triangle. The Lesum, and its tributaries, the Wümme and Hamme, the Schönebecker Aue and Blumenthaler Aue, are the downstream tributaries of the Weser. The city's municipal area is about long and wide. In terms of area, Bremen is the thirteenth largest city in Germany; and in terms of population the second largest city in northwest Germany after Hamburg and the eleventh largest in the whole of Germany (see: List of cities in Germany). Bremen lies about east of the city of Oldenburg, southwest of Hamburg, northwest of Hanover, north of Minden and northeast of Osnabrück. Part of Bremerhaven's port territory forms an exclave of the City of Bremen. Hills of Bremen The inner city lies on a Weser dune, which reaches a natural height of 10.5 metres (34 feet, 6 inches) above sea level at Bremen Cathedral; its highest point, though, is 14.4 metres (47 feet, 3 inches) above sea level and lies to the east at the Polizeihaus, Am Wall 196. The highest natural feature in the city of Bremen is