Map of the territory of the free imperial city of Bremen in 1798. The walled city of Bremen proper is the brownish area near the center of the map. The map, published by C. H. Heineken in 1798, is based on a trigonometric survey. The map is titled "Map of the territory of the Imperial and Hanseatic city of Bremen, including the villages whose sovereignty, with the exception of certain privileges, was ceded to the Electorate of Brunswick in 1741".