The German–Spanish Astronomical Centre at 2170 m altitude on Calar Alto in the Sierra de los Filabres, Andalusia, Spain. It was founded in 1972 and is operated jointly by the Max-Planck-Institut für Astronomie, Heidelberg, and the Instituto de Astrofísica de Andalucía (CSIC), Granada. Its largest instrument is a 3.5-m reflector, opened in 1984. There are also a 2.2-m reflector, opened in 1979, and a 1.23-m reflector, opened in 1975. A 0.8-m Schmidt was moved to Calar Alto in 1980 from Hamburg, where it had been used since 1955. Since 1978 Madrid Observatory has also operated a 1.5-m reflector at the site.
http://www.caha.es/ Official observatory website.