The Maryland Science Center is the Inner Harbor's family-oriented science museum, with an IMAX theatre, a planetarium, and three floors of interactive exhibits covering astronomy, earth sciences, dinosaurs, and physics. It is primarily aimed at children but adults without children will find the dinosaur wing and the astronomy exhibits engaging.
The rooftop observatory is open on certain evenings for free public telescope viewing — worth checking the schedule if you are interested in stargazing. The building is directly on the Inner Harbor waterfront, which makes the views from the upper floors an unexpected bonus.