Last month I bought a new Cannondale bike and love it! I just wish I got to ride it more often but last Sunday I got to take nice long circuit loop. I started at my apartment and rode the little more than mile and a half to the Mount Vernon Trail, which I picked up around mile 7.5. Just before mile 13, you will see a marking for Four Mile Run. That creek is nothing to write home about, but there is a nice little trail aside it called, well, the Four Mile Run Trail. I'm not sure how long it is, but while wind-prone along Glebe Road in Arlington, is a pleasant trail.
A really cool thing, the trail goes right under I-395 now and bypasses most of the condos and restaurants in Shirlington! I know because I beat the ribbon cutting too!. Now I'd love to be a condo owner, and restaurants are good, but the new path is more direct to the W&OD Trail (click for access points). Not to mention that you don't have to ride on a bunch of side streets and up and down a Z shaped ramp to cross the I-395 overpass. No more!!! I rode the W&OD, which parallels the Four Mile Run, until the Falls Church / Arlington Border at Mile 5.5 or so.
The Custis Trail was next, I picked that up at Mile 4.0. This trail is quite challenging for an "urban/suburban" trail, lots of short, rolling hills but hills nevertheless. It's really challenging to run on in the summer humidity. But I survived and was doing okay. Then the wind picked up after I left the Custis Trail. I ended up stopping my ride at the airport since I was tired but satisfied with my ride. Had I not made a dumb turn on to the Roosevelt Bridge thinking I was going to ride to L'Enfant and call it a day, it would have been about a, let's see, 8.5 miles or so until the W&OD plus 7 miles on W&OD plus 4 miles on Custis plus 4 on Mount Vernon = 23.5 mile loop. But my collection of wrong turns added 3-5 miles to that plus a crossing on the Memorial Bridge.
As I continue with my fitness travels, I may become brave enough to try the W&OD Trail all the way to Purcellville and back, 89 miles. There's a ways to go before I get there, but I finally have a bike to take on a ride that long.