The Urania Sternwarte, opened in 1907, is the oldest public observatory in Switzerland and one of the few in any city centre still genuinely used for star-gazing rather than as a curiosity. The big refractor telescope — a 1907 Zeiss 30 cm — sits in a green-domed cupola on top of the Urania tower above Bahnhofstrasse, and astronomer-guides open it for evening viewings most clear nights.
Sessions last about 90 minutes; the guide picks targets to suit the season (Saturn's rings, the Moon's craters, double stars, distant nebulae if the city light cooperates). The tower also has a small exhibition on Zurich astronomy and a viewing platform at 51 metres that opens onto a panorama of the old town rooftops. Tickets must be booked online a day or two ahead; sessions are in German with limited English support. A genuinely special evening if the sky cooperates.