Ely

The lantern of the 14th century octagon tower of Ely Cathedral.

The octagon was rebuilt by sacrist Alan of Walsingham between 1322 and 1328 after the collapse of the original nave crossing on 22 February 1322. Ely's octagon is considered "one of the wonders of the medieval world". Architectural historian Nikolaus Pevsner believes the octagon "is a delight from beginning to end for anyone who feels for space as strongly as for construction" and is the "greatest individual achievement of architectural genius at Ely Cathedral"

https://en.wikipedia.org/wiki/Ely,_Cambridgeshire

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