Gerogetown-Rowley State Forest
Georgetown-Rowley State Forest at 1000 acres hosts miles of interesting trails. It is one of only two state forests in Massachusetts that is split by an highway, Route 95, and connected by a trail bridge. The other being The Blue Hills Reservation, Route 24.
If Georgetown-Rowley's trail aren't enough you can easily connect them to Cleaveland Farm State Forest, Willowdale State Forest and Bradley Palmer State Forest. That would be enough riding to force most people to get a motel room.
The trails at Georgetown-Rowley range from easy degrading doubletracks to fun but not too challenging singletracks. It would be difficult to ride Georgetown-Rowley's trails in any consistant order. So expect to do some exploring.
With experience, you'll be able to put together an awesome ride that you'll no doubt share with your friends.