The Grüne Zitadelle is the last building designed by the Austrian artist and architect Friedensreich Hundertwasser, completed in 2005 after his death. It is, characteristically, impossible to mistake for anything else: a pink-and-ochre blob of a building with golden onion domes, undulating facades, trees growing from balconies and rooftops, and not a right angle to be found anywhere. Hundertwasser called it an "oasis for humanity and nature in a sea of rational houses."
The building is a functioning residential and commercial complex — apartments, offices, shops, a hotel, a cafe, and a theater are all inside. The interior is equally idiosyncratic: irregular floors, mosaic-covered columns, and rooms that seem to have grown organically rather than been designed. Guided tours run through the public areas; the courtyard is free to enter during the day.
Whether you find it delightful or alarming, it is genuinely unlike anything else in Germany. It stands on the Breiter Weg, Magdeburg's main shopping street, making it unavoidable if you walk the city center.