Moorfields was an open space, partly in the City of London, lying adjacent to – and outside – its northern wall, near the eponymous Moorgate. It was known for its marshy conditions, the result of the defensive wall acting like a dam, impeding the flow of the River Walbrook and its tributaries. Moorfields gives its name to the Moorfields Eye Hospital which occupied a site on the former fields from 1822–1899, and is still based close by, in the St Luke's area of the London Borough of Islington.