What are you into? I'd say if you want to stay downtown do Ft McHenry, aquarium, Walter's Art Museum. AVAM is good. I really like Baltimore Museum of Industry and B&O Museum but might not be for everyone. Visit Fells Point. Mt. Vernon for nice neighborhood strolls to enjoy the architecture. Rawlings Conservatory is a pita to get to but really cool and often overlooked. A couple cool house museums are Mt Clare, Evergreen, Homewood.