North of Exeter in the Henderson-Swasey Town Forest, the Fort Rock Trail System offers a great mix of terrain and a variety of trails to explore. The forest has a network of trails with plenty of rocky, rooty, challenging single track trails. Make sure to check out the portion of the trail system that is on the north side of SR101, as well (there is a large culvert under the highway).
To reach the mountain biking trailhead from Manchester, head east on SR101 to Exit #10. Head south on SR85 for 0.3 miles. Just before the railroad bridge, turn right on unsigned dirt road into the town forest. Head up the hill into the parking area.
Overall, Fort Rock Trail System is the 21st most popular mountain bike trail of all 24 mountain biking rides in New Hampshire.