You can't leave Baltimore without trying crabs made in traditional Chesapeake fashion—steamed with Old Bay seasoning. Captain James Crabhouse has waterfront seating and even a menu with a "Crab Picking 101" tutorial to help the novices.
Crabs are purchased by the dozen and priced by size and dumped on the brown paper spread out on your table. A tip to the Non-Marylanders: buy some sides (fries, hush puppies, corn, etc.) because after a while your fingers not accustomed to crab picking will get tired. With crab-picking, you'll burn more calories trying to get at the meat than you'll take in from the crab. But it's oh so worth it.
Also, don't wear your nice clothes, because you'll have Old Bay all over you by the end of the meal.