The West Yorkshire Built-up Area, previously known as the West Yorkshire Urban Area is a term used by the Office for National Statistics (ONS) to refer to a conurbation in West Yorkshire, England, based on the cities of Leeds, Bradford and Wakefield, and the large town of Huddersfield. It is the 4th largest urban area in the United Kingdom. However, it excludes other large towns and suburbs such as Castleford, Pontefract and Wetherby which, though part of the county of West Yorkshire are considered independently. There are substantial areas of agricultural land within the designated area – more than in any other official urban area in England – many of the towns and cities are only just connected with one another by narrow outlying strips of development.