Lake Drummond (above) is one of only 2 natural lakes in Virginia. It sits in center of the swamp, virtually untouched. It's not easy to get there. The shortest way by bike or on foot is down Washington Ditch. I like riding from the Jericho parking lot, heading down Lynn Ditch to Washington which gives round trip of about 16 miles to lake and back. The only way to get there by car is to use the Interior Ditch, and by canoe, kayak or small boat through the Feeder Ditch.
Information about the Virginia side
Information about the North Carolina side
There is a Dismal Swamp Canal Trail that is easily confused with all of this. The Canal Trail is a paved trail that runs on the far eastern border of the swamp (see map). You cannot get from that paved trail to any of the dirt trails unless you get off your bike and get into a boat.
This is Bethany on Washington Ditch. It's the most recent picture I have, taken in December 2014.