Lake Fairfax singletrack loop consists of 2.7 miles of forested singletrack loop that has some climbs & several log crossings.
From Leesburg Pike 7 go 1/4 mile south on Baron Cameron Ave, turn left onto Lake Fairfax Dr. and drive south about 1 mile to parking area.
http://www.singletracks.com/item.php?c=1&i=3515