Barnack Hills & Holes is a 23.3-hectare (58-acre) biological Site of Special Scientific Interest in Barnack in Cambridgeshire. It is also a national nature reserve. It is a Nature Conservation Review site, Grade I. In 2002 it was designated as a Special Area of Conservation, to protect the orchid-rich grassland as part of the Natura 2000 network of sites throughout the European Union.