Ely ( ) is a cathedral city in Cambridgeshire, England, 14 miles (23 km) north-north-east of Cambridge and about by road from London. Æthelthryth (Etheldreda) founded an abbey at Ely in AD 673; the abbey was destroyed in 870 by Danish invaders and was rebuilt by Ethelwold, Bishop of Winchester, in 970. Construction of the cathedral was started in 1083 by a Norman abbot, Simeon. Alan of Walsingham's octagon, built over Ely's nave crossing between 1322 and 1328, is the "greatest individual achievement of architectural genius at Ely Cathedral", according to architectural historian Nikolaus Pevsner. Building continued until the dissolution of the abbey in 1539 during the Reformation. The cathedral was sympathetically restored between 1845 and 1870 by the architect George Gilbert Scott. As the seat of a diocese, Ely has long been considered a city; in 1974, city status was granted by royal charter.