This is the weekend of DC’s twice yearly “WalkingTown” program: “Join Cultural Tourism DC for more than 80 free walking tours (and a few bike tours) in 18 neighborhoods across Washington, DC.” I’ve done these before, and they’ve been well worth my time.  They typically concentrate on a neighborhood’s history, or follow a theme (Civil War cemeteries, public works, new development plans, etc.).  Most are just walkup, but a few require reservations.  If you’ve got a couple free hours this weekend, take a look at the schedule and see if something catches your fancy (for cyclists, I particularly recommend the Anacostia/Riverwalk ride).