The White Loop is a nice introduction to the Schaeffer Farms trail system. It's flowing and rolling singletrack through hardwood forest.
The loop can be ridden in either direction and has multiple shortcuts (Orange - Intersection 2 to 7
, Orange - Intersection 3 to 5
) back to the parking lot. In addition, there is a connection to the new Seneca Ridge Trail
which will lead you out of the park.