Rocky technical terrain, single track, double track. The local bookstore in Gloucester has a map published by the Dogtown committee. Use the map as a general guide though as only some of the trails appear on the map. Follow to north and north west to find great single track. Dogtown is mostly geared toward intermediate to advanced riders.
Most hills are difficult due to technical terrain more than grade.
For a good ride head northwest towards Norton's tree farm or northeast toward Steel Derek Quarry. There's lots of rocky single track that will challenge any hardtail rider. Great ten mile loop. Park at the gate next to water tower. The pipeline in Gloucester.