From the Wikipedia page [1]
The main areas of open space are:
- Bentley Priory, Stanmore: 165 acres (66ha) open space; Site of Special Scientific Interest and Local Nature Reserve
- Canons Park: 45 acres (18ha) 18th century parkland
- Grim's Dyke Open Space, Harrow Weald
- Harrow Weald Common, Harrow Weald
- Headstone Manor Recreation Park: Template under construction. including the Museum and Headstone Manor & Bessborough Cricket Club
- Pinner Park Farm tenant dairy farmers Hall & Sons: total {230 acre}
- Stanmore Common: 120 acres (48ha); Local Nature Reserve
- Stanmore Country Park: 77.5 acres (31ha); Local Nature
- Streamside Reservation, alongside Yeading Brook, Pinner