4. Rosslyn
Average home price per square foot: $498
Difference from county average: +$90
Stroll across the Key Bridge and voila — you’re in Georgetown. That’s why Rosslyn is often called the Gateway to the District (it even has a public park by that name). Dense and urban, Rosslyn offers city-style living. A county master plan is making its streets more pedestrian-friendly with the introduction of wider promenades, new public art, Arlington’s first parklet, and events ranging from beer tastings to music festivals. Some of its high-rise penthouses, with their enviable views of D.C., are among the highest-priced homes in the county.