23/24 Leinster Gardens
At first glance 23/24 Leinster Gardens, Paddington, London looks just like the other houses in the street

but there is a clue in the windows. It is not a house at all; just a facade. The original house was pulled down and replaced with a facade in the 1860s when the London Underground Metropolitan line was built and it was necessary for the trains to have a place to let off steam.
