The Inner Harbor of Baltimore is a fantastic place to visit but don't overlook Fort McHenry, located at the tip of the Federal Hill part of town. The easiest way to get there is by water taxi. It only costs $8 for an all-day pass on the water taxi but if you plan on seeing things in the Harborplace area go for the $18 ticket which includes not only the water taxi day pass but also admission to all the ships (Constellation, Torsk, Chesapeak Lightship, etc.).
The water taxi leaves you off at the dock where you board a bus for a short (5 minute) ride to the fort. Upon entering the reception building it will cost an additional $5 if you want to enter the actual fort. While you may walk around the surrounding area that includes live re-enactments of day-to-day life (mess tent, drills, etc.), the small fee is more than worth the experience of being inside the actual fort. The main focus is, by its sheer size and beauty, the 13 star flag on the pole that is situated exactly where the inspiration for Francis Scott Key's "Star Spangled Banner" once flew. Not only can you go into the re-created barracks that the soldiers once lived in, you also have the opportunity to see the Commanding Officer's quarters and all other aspects of what it was like to actually be stationed at the fort. The best part, at least for me, was being able to stand on top of the wall and look out into the bay and realize what it must have been like watching approaching warships bearing down on the fort. Don't forget to take a close look at the cannons and how they were mounted.