Baltimore- one morning to ride, Where should it be?

We are staying in Baltimore for one evening and have time for a morning bike ride of several hours the next morning. Any suggestions?

Gwynns Falls Trail-- http://www.gwynnsfallstrail.org/ You'll get to see everything from shady Leakin Park all the way through downtown. Good signage, and from the downtown section you can ride around Inner Harbor or take the off-shoot out to Fort McHenry.