There's a community center on Lewinsville Rd (sort of behind Tyson's Corner) that has a pool, and they should have drop-in hours. there's a map in the address at the top of the page.

http://www.fairfaxcounty.gov/parks/rec/shillrec.htm

If you're closer to falls church, then maybe search in Fairfax Co Parks website for another fitness center.

Alternately, do you belong to a gym that has reciprocity at other gyms?

http://www.swimmersguide.com/

This is the best pool finder I have found. It shows the community center that tri-ac listed as well as Skyline Sport and Health club.

http://www.sportandhealth.com/club.aspx?id=258&sn=102

Lived in that area awhile back.

Where to park along the bike trail kind of depend on where you hit it at... Its a long trail. Although I don't recall seeing designate parking areas. Most people probably bike or run from their home to the trail. Further out, or closer in to DC you'd find some parking.

Anyway, assuming you are going to be in the vacinity of Route 7 (which runs from Falls Church to Tysons), I would park in the shopping center lot associated with the Giant Food store near where Route 7 crosses the bike path. Maybe you are not techncially supposed to do that, but if you park at the end closer to staples and closer to the path(near the intersection of route 7 and west st) I doubt anyone will notice/care. Oh there is a small parking area just off west street but at last check I think it was big enough for maybe ten cars.

As for swimming that's a little tough. DC has a pretty good system if you don't mind going to the city. You can track them down on the web. And I've not been there yet, but if you don't mind driving out past Manassas to the Freedom Aquatic Center it looks pretty cool and reasonable one time charge. I think it is associated with George Washington or George Mason University. Which also might have a pool right in Fairfax.

Finally check out DCRainmaker's blog. That dude is swimming, biking, and running all of the area and you might be able to get some clues from him.

Lived in that area awhile back.

Where to park along the bike trail kind of depend on where you hit it at... Its a long trail. Although I don't recall seeing designate parking areas. Most people probably bike or run from their home to the trail. Further out, or closer in to DC you'd find some parking.

Anyway, assuming you are going to be in the vacinity of Route 7 (which runs from Falls Church to Tysons), I would park in the shopping center lot associated with the Giant Food store near where Route 7 crosses the bike path. Maybe you are not techncially supposed to do that, but if you park at the end closer to staples and closer to the path(near the intersection of route 7 and west st) I doubt anyone will notice/care. Oh there is a small parking area just off west street but at last check I think it was big enough for maybe ten cars.

As for swimming that's a little tough. DC has a pretty good system if you don't mind going to the city. You can track them down on the web. And I've not been there yet, but if you don't mind driving out past Manassas to the Freedom Aquatic Center it looks pretty cool and reasonable one time charge. I think it is associated with George Washington or George Mason University. Which also might have a pool right in Fairfax.

Finally check out DCRainmaker's blog. That dude is swimming, biking, and running all of the area and you might be able to get some clues from him.

Btw. Don't worry about safety you'll be fine.

Sorry for the multi post, I'm on blackberry. Which, for safety around the DC area, I guess be careful you don't hit someone on BB who is not looking where they are going.

A couple of quick random thoughts:

1) Swim: Tons of options with Fairfax rec centers. I often swing by Audrey Moore at Wakefield, as they have a nice 50m pool that's cut up into about 14 lanes, so always lanes to swim. Also, if you want a fun experiance, check out GMU's aquatic facility, awesome stuff (50m pool setup long course, plus a shorter pool).

2) Bike: While W&OD is functional, it's best to go westbound and get beyond Reston, where it opens up a bit more. My real favorite location is down off I-95S at exist 150ish, Prince William Forest Park, a great 7m loop with good rollers and a section dedicated to bikes. I write about it a fair bit, so just search for that on my blog to find tons of pictures.

3) Run: A world of awesome places to run. My favs: W&OD, Four Mile Run, GW Parkway, The Mall, Canal, Custiss trail. Depending on how far you want to go, you can do a ton of great runs from the Tysons area heading towards DC.

Falls Church is a nice place to be based out of from a trail perspective, it's pretty central.