Revel in laziness at Butts Tubes near Harpers Ferry and rent an inner tube (from $27) and a floating cooler ($15)—score beer and ice at the adjacent general store. A van will transport you to the mouth of the Shenandoah River. For the next two hours, slip under bridges, gaze up at cliffs, and stop to tan on the flat rocks midstream.
Paddle through tony Georgetown in your kayak from the Thompson Boat Center. Get great views of the Watergate complex, Kennedy Center, and Theodore Roosevelt Island Park. If you’ve got the arms for it, you can even paddle right up to the steps of the Jefferson Memorial.
Hit the hills with the Capital Hiking Club, a nonprofit organization that runs weekly guided hikes through the forests and beaches of Appalachia (from $28). Catch a bus from D.C. to your destination, including Shenandoah National Park or Maryland's Calvert Cliffs.