Opened in late 2005, the Grüne Zitadelle is one of the last projects designed by Friedensreich Hundertwasser, an Austrian artist who died in 2000. Here, the artist wanted to create "an oasis for man and nature in an ocean of rational houses". This architectural complex, the construction of which was extremely controversial, is now home to several dozen apartments, shops, offices and a hotel, as well as a permanent exhibition of works by Hundertwasser himself.