The regional science centre fills four floors of a former bank just east of the main pedestrian street, packed with interactive exhibits on physics, biology, energy, and astronomy. It is squarely aimed at families with school-age children, with the expected button-pressing and pulley-hauling, but adults who like that sort of thing will find plenty to play with — the planetarium and the optical illusions room in particular.
Open daily, with longer hours in school holidays. If you are travelling with kids and the weather turns, this is one of Trondheim's safer bets for a rainy afternoon.