Stefanik Observatory

The Štefánik Observatory (Štefánikova hvězdárna) is an active public astronomical observatory on Petřín Hill, founded in 1928 by the Czech Astronomical Society and named after Milan Rastislav Štefánik — Slovak astronomer, general, and co-founder of Czechoslovakia. Its centrepiece is a 1905 Zeiss double refractor weighing 5.5 tonnes, purchased with a contribution from President Tomáš Masaryk and still in use today following a renovation completed in 2024. The observatory has three domes housing different telescopes and an observation house with a retractable roof; on clear days visitors can observe the Sun and its sunspots through guided telescope sessions, and in the evenings the Moon, planets, star clusters, and galaxies. Unlike most observatories, no booking is required — visitors simply arrive during opening hours and are guided by staff astronomers. A permanent exhibition on astronomy and a themed Astrobistro café are also on site.