The Mercer and Fonthill Museums were started by the historian Henry Mercer at the start of the 20th century to collect examples of handmade items and crafts that were dying out after the Industrial Revolution. He collected over 30,000 pieces and, in order to display them all, built a museum to house them in.
But this was no ordinary museum: in 1916 he built a 6 storey tall castle out of concrete. Indeed, he had earlier built a smaller one as his home (which became the Fonthill museum)
View from the street; larger version here.
Opposite side; larger version here.
Apart from being a huge manor house filled with a strange collection all from a single determined collector, which I hope sounds intriguing enough for someone to start building a game, the museum has a second appeal. The museum’s guide book includes floor plans: with just a little editing, these could be used to create maps for this museum/castle location.