Nottingham is a city, unitary authority, and county town of Nottinghamshire in the East Midlands of England. The centre of Nottingham lies on the River Leen and its southern boundary follows the course of the River Trent, which flows from Stoke to the Humber. According to the 2001 census, Nottingham had an estimated city population of 275,100 which increased to an estimated 278,700 in 2005. The Nottingham Urban Area conurbation (which includes surrounding suburbs outside the city boundary such as Arnold, Carlton, West Bridgford and neighbouring towns) has a population of 666,358 (2001 figures). Nottingham is a member of the English Core Cities Group.