Middlesbrough is a large town in the Tees Valley sub-region of the North East of England. It is the largest and most populous settlement within the borough of Middlesbrough, which encompasses the town and several outlying villages which have become suburbs. Historically part of the North Riding of Yorkshire, in 1968 the town became the centre of the county borough of Teesside, which was absorbed by the non-metropolitan county of Cleveland in 1974. In 1996 Cleveland was abolished, and the Middlesbrough borough became a unitary authority, within the ceremonial county of North Yorkshire. Middlesbrough is different from the other districts on Teesside, as the borough is almost entirely urbanised, thus making it the largest town in terms of area and population, but the smallest district. However, the areas of Eston, Grangetown, Normanby, Ormesby, and South Bank in the neighbouring borough of Redcar and Cleveland, are also part of the Middlesbrough agglomeration. Middlesbrough is situated on the south bank of the River Tees, a few miles from the edge of the North York Moors National Park. Teesport is the UK's second largest port, lies 3 miles to the east, and Durham Tees Valley Airport lies 8 miles to the west, near Darlington. North east of Middlesbrough, the Tees Estuary with its colony of breeding seals, has extensive sandy beaches in both directions. Some 7000 salmon and 13,000 sea trout migrated upstream through the estuary in 2000. More on Middlesbrough