I spend a lot of time, perhaps too much, thinking about the lost architecture of Britain.
Crystal Palace was the most tremendous loss of the modern era, yet it's rare to see any pictures of it. When built in 1851, it was the largest building in the world and three times the size of St Paul's Cathedral.
What's more, that immense ironwork and 293,000 glass panels went up in just 190 days for the World's Fair. Almost 1 million square feet of glass. An extraordinary feat.
It was razed in a fire in the 1930s and never rebuilt.