I try to stay on the Virginia side of the Potomac, as otherwise it encourages the Maryland Democrats.
Probably will be making a visit to the Old Europe in January, as we have been discussing meeting a family friend there.
I will put a recommendation in for The Hermitage, in Clifton VA which is located about a quarter mile from my house. It's as good as any K Street establishment you will find. It isn't cheap, but first class food and a very scenic location. It's an old hotel, built in the 1860's that has been completely restored.
http://www.hermitageinnrestaurant.com/
The town of Clifton is also quite historic, most of the houses are from the 1850-1900 period, with the oldest from the Revolutionary War period, so walking around the town is worthwhile.
For a less expensive Clifton alternative, the Heart in Hand
http://www.heartinhandrestaurant.com/Index.htm is diagonally across the railroad tracks from the Hermitage. It's in an old feed and grain store, built before 1900, and redone, but still with wide pine plank floors, etc. Quite charming. Nancy Reagan and George Will would occasionally meet there for lunch when RR was in office.
Jack