Milton Keynes is a large town in Buckinghamshire, England, about 50 miles (80 km) north-west of London. It is the principal settlement of the Borough of Milton Keynes, a unitary authority. The River Great Ouse forms its northern boundary; a tributary, the River Ouzel, meanders through its linear parks and balancing lakes. Approximately 25% of the urban area is parkland or woodland and includes two SSIs.