Arlington Down by the River Potomac Overlook Regional Park
It’s easy to search no further than the nature center and gardens in this park. But don’t overlook the 70 acres of woodlands crisscrossed by hilly paths that ford babbling Donaldson Run. Spots are deep enough for your dog to paddle, and some trails are good for rock-hopping; one descends under GW Parkway to the view that gives the park its name. The return loop ascends a staircase to a former Indian village, an orchard, and a butterfly garden.