An astronomy museum and working observatory built into a 16th-century bastion of Utrecht's old city walls. The combination is unexpected and charming: medieval brick fortifications housing telescopes, planetarium shows, and exhibitions about the universe. The bastion itself, one of the few surviving sections of the old defences, sits on the bank of the Singel moat.
The museum covers the history of astronomy at Utrecht University — which has been observing the skies from this spot since the 1850s — alongside broader exhibitions about space and cosmology. On clear evenings, the observatory opens its domes for public viewing sessions through historic and modern telescopes. The rooftop terrace offers good views over the old city. A quirky, under-visited museum that combines Utrecht's military and scientific history in one compact package.