Milton Keynes, locally abbreviated to MK, 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. At the 2011 Census, its population was almost 230,000; the Office for National Statistics estimates that it will reach 300,000 by 2025. 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 an SSI.