More than 800 caves have been mapped beneath Nottingham, used over the centuries as tanneries, malting cellars, wine stores, public-house cellars, slum dwellings, and air-raid shelters. The City of Caves attraction, hidden incongruously beneath the Broadmarsh shopping centre, takes you through a representative few on a 45-minute guided tour: a medieval tannery with its still-visible vats, a slum cottage, and a Second World War shelter where families spent the worst nights of the Nottingham Blitz.
It's not visually grand — these are working caves, not crystal grottos — but the guides are good and the layered history is more memorable than the castle above. Tickets are timed and can be booked online.