Single track. there are several loops, so the 4 mile distance is a bit deceptive. A portion of the trail veers off toward Harry S. Truman Pkwy, and I followed that for a few miles as well. This is the best part of the trail - very ridable, but it needs to be ridden more (overgrown in some spots). Fall would be the best time to ride this area.
The trail follows the South River for a little while - the trail is on a very NARROW ledge. At times the drop to the river is a bit spine tingling even though the trail itself is relatively easy (it has its spots though!).
There is a steep section with some gnarly roots - this is really the only technically challenging part of the trail. Good pratice for beginners, without being suicidal!
A good short course if you are pressed for time and live in Annapolis.
How to get there:
US Route 50 to MD 665. Go south on Riva road about two miles to Annpolis Senior High School (on the right). There are several trail heads, the best one (the rooty section) is in the right corner of the athletic fields behind the school. the loops go to the left from this trail head, and the unexplored area I mentioned is to the right.
Don't ride on the althletic fields. Go around the edge of the field.