Time Out says
The Urania is Zurich’s astronomical observatory. There are tours on three evenings each week, plus monthly special tours for children. The tours are in German.
Operating since 1907, the Urania has been Zurich’s astronomical observatory for over a hundred years. Though designed to offer a look through a telescope to the common people, it is not open at all times. There are three public tours per week on Thursday, Friday and Saturday evenings, and special tours for children once a month. All public tours are in German, but private tours in English can be arranged.