The Fredericksburg Battlefield Visitor Center is located at the base of historic Marye's Heights on the Fredericksburg battlefield. There are four walking trails that will be mapped out for you here. My favorite is Lee Drive, where you see the fort from where General Lee kept watch over the river. It's a trail that takes you back in time, with large pictures, original trenches, and a great granite pyramid built as a marker along the railway line to note the historical site. If you're interested in civil war history, they also have reenactments periodically that are very nicely done.
The website at http://www.nps.gov/frsp/fburg.htm is the national park website that gives you all the details you will need to plan your visit to this historical area.
Bring a picnic lunch and make a day of the journey through time.