Washington DC has a quite few options for urban running.
The obvious are Rock Creek Park, the Mall, East Potomac Park (a 5k loop which has Haines Point) and West Potomac Park (which you can create an almost 4 mile loop by crossing the Memorial Bridge, connecting to the Most Vernon Trail and then cross back over the 14th Street Bridge). You also have the trial at Theodore Roosevelt Island. There is also the ever popular Mount Vernon Trail just across the Potomac River in Virgina.
The hidden gem in DC is the Anacostia River Trail. Using the various Anacostia River crossings you can create 4 mile, 6 mile or 7 mile loops. At Benning Road you can continue on the trail to hook up with the other trails that could take you Greenbelt, MD.
You can really explore a lot of local trails in the various metro areas with the All Trails web site (
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