This former autonomous Danish city was annexed by the Nazis in 1937. The most heavily-populated part of Hamburg, it is a multicultural working-class neighborhood. Architecture junkies will love the "Kontorhäuser," the renovated factories, the imposing classical Palmaille and the exquisite villas on Elbchaussee. The Altonaer Rathaus is built in the typical style of the Wilhelmenian era (1888-1918).