European Observatories From Leiden in 1633 to Haute-Provence in 1937

Leiden Observatory was established in 1633 to house the quadrant of Willebrord Snellius, which makes it the oldest continuously operating university observatory apart from the Vatican Observatory. Its directors included Willem de Sitter, Ejnar Hertzsprung and Jan Oort, and since the 1974 move to the science campus its astronomers work mainly on data gathered remotely.

Brera was built in 1764 inside the Palazzo Brera in Milan by the Jesuit astronomer Roger Boscovich. Control passed to the Austrian Habsburgs after the Jesuits were suppressed in 1773 and to Italy in 1861, and Giovanni Schiaparelli used its 8-inch refractor, installed in 1875, for his Mars observations.

Dunsink was established in 1785 outside Dublin with an endowment from Trinity College Dublin. William Rowan Hamilton directed it from 1827 to 1865, and on a walk into the city in 1843 he conceived of quaternions; its 12-inch Grubb South Telescope was completed in 1868.

The Naples observatory on Capodimonte hill was founded on 4 November 1812 and is described as the city's oldest scientific institution. Its neoclassical building was completed in 1819 and first housed a 17.5-centimeter Fraunhofer refractor, the largest refractor built up to that time.

Hamburg Observatory was founded by the city in 1825 and rebuilt in the Bergedorf district in 1912, and the university has run it since 1968. Walter Baade discovered the near-Earth asteroid 1036 Ganymed there on 23 October 1924, and its 1-meter reflector, first used in 1911, was then the fourth-largest reflector in the world.

The Royal Observatory of Belgium was founded in 1826 by King William I of the Netherlands at the urging of Adolphe Quetelet, and has stood in Uccle, Brussels, since 1890. It has discovered 13 minor planets and has hosted the World Data Center for the Sunspot Index since 1981.

Arcetri was founded in 1869 in the hills near Florence, close to the villa where Galileo spent his last years. Today it is an astrophysical research observatory that builds instruments for major telescopes, including the MMT, the Large Binocular Telescope and adaptive optics for the Very Large Telescope.

Pic du Midi sits at 2,877 meters in the French Pyrenees and was taken over by the French state in 1882. Observations there disproved the Martian-canal hypothesis in 1909, and its main instrument today is the 2-meter Bernard Lyot Telescope, installed in 1980.

This Potsdam-Babelsberg institute was formed in 1992 as successor to the Berlin Observatory of 1700 and to the Astrophysical Observatory Potsdam of 1874, the first observatory devoted explicitly to astrophysics. Berlin astronomer Johann Gottfried Galle discovered Neptune in 1846, and the grounds hold the Einstein Tower, built from 1921 to 1924.

Nice Observatory on Mont Gros was financed by the banker Raphael Bischoffsheim and founded in 1879, with a dome engineered by Gustave Eiffel. In 1886 it unveiled the 77-centimeter Grande Lunette, then the largest refracting telescope in the world.

Ondrejov was founded in 1898 as a private facility by the amateur astronomer Josef Jan Fric and donated to the Czechoslovak state in 1928. Its 2-meter telescope, added in 1967, is the largest in the Czech Republic, and the observatory has discovered more than 700 minor planets.

Haute-Provence was established in 1937 as a national facility for French astronomers, chosen for about 170 fully cloudless nights a year. There in 1995 Michel Mayor and Didier Queloz used the ELODIE spectrograph to discover 51 Pegasi b, work that earned them half the 2019 Nobel Prize in Physics.