There are a whole group of wonderful open spaces in and around the Tewksbury State Hospital, including the Pinnacle Trail, the Pines Cemetery Trail and Side Loop, The State Hospital Trail, and Pines Cemetery Main Trail. You can get a quick overview from this Tewksbury map page.
More Resources:
Town of Tewksbury PDF Map
A full set of trail maps for all of Tewksbury.
All Trails for Tewksbury Hospital Trail
Trails maps and more info.
Wikipedia
The full story and difficult history of the hospital