Okay, I've got a bunch of comments.
1. Vienna, VA (and the surrounding area) is extremely safe. You're talking all upper-middle class neighborhoods with expensive houses. In fact, you're more likely to have a police officer/unit stop your shoot to ask what you're doing than you are likely to see any potential threat.
2. Landmark is a shopping mall with a big parking deck. I wouldn't go there b/c I believe mall security patrols the lots and garage and it's all private territory so they could stop you from shooting.
3. Here are a couple of locations to check out:
--Industrial Road in Springfield (inside the Beltway and north of I-95/395, near Backlick Road). It's a lot of old industrial parks, the abandoned Washington Gas headquarters (which is fenced up), a small gravel quarry...definitely a gritty, work (as opposed to residential) feel and not many people around on a weekend.
--If you are willing to do a parking garage and you want something close by, then try the parking deck at the Vienna Metro.
--In Fairfax City off of "Old Picket Road" (which branches off of "Pickett Road" and is near Fairfax Circle and a Home Depot), there is a safe yet very gritty area with a gravel plant that I believe is closed on weekends, next to a Volvo repair shop and a Home Depot. If that doesn't work for you, around Fairfax Circle there are a series of small businesses...I'm thinking particular of a marble counter shop that has a bunch of dust and rubble in front of their gates with lots of space in the parking lot before the gates. Definitely an abandoned or decayed look to it.
--Check out behind the Home Depot in the Mosaic District off of Lee Highway in Merrifield. It is full of small businesses (furniture repair, granite counters, industrial lighting). Some look very gritty, not much in the way of signage, lots of parking lots, many will be closed on a Sunday or even a Saturday (since some of them are BtB). This is pretty close to Vienna btw.
Now, be warned...there are plenty of places that look industrial or abandoned. But this is Northern Virginia. Property is worth a premium. So there are people everywhere. If you're thinking of doing a shoot with a beautiful girl in lingerie perched on top of a 57 Camaro, you will draw a crowd in any built-on space you go in Northern Virginia.