Hello, and welcome.
Like mentioned there are plenty of lakes in Reston. Some are public, some are private. Some that are public have very limited access without a boat.
Goose Creek is a favorite spot of mine, I have been a pond fisherman my whole life but really got into smallies last year. Goose is a great spot for them all summer, but as the year goes on and the water levels drop the fatties tend to 'migrate' into the river (I fish in a section that is very shallow, and is <1.5mi from the Potomac River). Where Goose and the Potomac converge I have always had a lot of luck. It's a bit of a hike but usually well worth it.
There's a park off of 'River Point Dr.' over there by Landsdowne, it's called Kipheart Bridge Park. Research it, and check it out when ALL OF THIS SNOW FREAKIN' MELTS. I'd be willing to meet you come summer time. I am always looking for new fishing partners. I like to fish a lil more than my friends.
Good Luck,
Snogle