The Greater London Urban Area is the conurbation or continuous urban area based around London, England, as defined by the Office for National Statistics. It had an estimated population of 8,505,000 in 2005 and occupied an area of 1,623.3 square kilometres (626.8 sq mi) at the time of the 2001 census. It includes most of Greater London, omitting some areas of countryside and small villages. Outside the administrative boundary it includes several adjacent areas of settlement and a few outliers connected to the urban sprawl by ribbon development. Its outer boundary is constrained by the Metropolitan Green Belt and it is therefore much smaller than the wider metropolitan area.