Westonbirt Arboretum is one of Britain's great tree collections, planted from the nineteenth century onward and now managed by Forestry England. It has thousands of species, long walking routes, and a canopy walkway that gives the place more shape than a simple park stroll.
Autumn is the famous season, but spring blossom and winter structure are also strong. It is about three miles southwest of Tetbury, so it works best by car, taxi, or bike rather than as a casual town-centre walk.