A genuine highlight of this area — free parking, toilets and picnic tables at Postern Hill (open 8am–7pm, gates locked overnight), plus paths good enough for pushchairs and little bikes alongside proper dense-woodland tracks for a longer walk. Trails aren't waymarked, so bring a map or download one if you're going deep into the forest.
2,750 acres of ancient forest a few miles south of Marlborough, believed to hold the highest concentration of veteran trees in Europe — including the Big Belly Oak, one of the oldest oaks in Britain. The forest takes in several named compartments (Knowle Hens Wood, Puthall Park among them), all connected by an extensive network of unwaymarked paths, tracks and rides.
Public forest — open access on the tracks; mind working-forest signs.