Dear Laaz,
the photos from that link I took 3,5 years ago during a visit at lake constanze. The collection of the mainau island was "reactivated" from italian sources in order to keep old tradition and rare citrus alive. Absolutely worth to visit. There is a little renaissance of old socalled Orangeries in Germany so that there are some others existing. Best collection you can find at Oranienbaum (south of Berlin), Potsdam (south-west of Berlin) and at Schwetzingen (near Heidelberg). They also keep a wider range of citrus varieties. Some pictures you can find at my webpage at
http://zitrusgarten.net/homepage/Orangerien/orangerien.htm
Best regards from Hamburg
Andy