This route mixes car-free sections of Beach Drive and the Bethesda Trolley Trail with low and moderate traffic roads to form an easy paved ride from DC to the Robert C. McDonnell Campground at Cabin John Regional Park.
There are plenty of options for customization, such as taking the roughly parallel Rock Creek trail for a slower but car-free alternative to the sections of Beach Drive and Jones Mill Rd that are open to cars.
For a much shorter route, take the metro red line to Grosvenor and ride the last 4 miles of this route to the campground.