I'm here for a work thing, only very briefly. But I have a few hours to kill before I need to head to the airport, so what should I check out?

I'm at the Inner Harbor, very close to the Aquarium, so I'm thinking I might head there. Seems like a good time. Other thoughts?

ETA: Thanks for the suggestions guise! I'm headed to the aquarium, and if I have time I might check out the art museum and/or Peabody library.

ETA2: The aquarium was lovely! I didn't know there'd be dolphins! DOLPHINS!