The Hispanic Astronomical Center in Andalusia (CAHA), also known as the Calar Alto Observatory, is the largest astronomical observatory in the European continent, located in Calar Alto, a plateau 2168 m high in the Sierra de Filabres, in the province of Almería, Spain.
Founded in 1973 following an agreement between the German and Spanish governments, the observatory has five telescopes with different apertures and optical systems, with the 3.5 m telescope being the largest telescope on the European continent. The observatory is jointly operated by the Institute of Astrophysics of Andalusia - CSIC and the Andalusian Government since 2019 and conducts cutting-edge scientific research in various fields of astronomy, such as the search for exoplanets, star formation, galactic structure, and cosmology.

The largest observatory in Europe, you must request observation time on one of its two main telescopes, the 2.2 m or the 3.5 m. You must be affiliated with a Spanish institution or apply through OPTICON ORP if you are from another European country. You can also purchase observation time if you have a very strong scientific case.
You must choose the observation mode: visitor or service. In the visitor mode, you travel to the observatory and operate the telescope. In the service mode, the observatory staff makes the observations for you. You must select the instrument, mode, and filters you want to use for each telescope, among those offered by the observatory on its website.