And an incredible amount of more london. Everything that gets knocked over gets buiilt on! There are at least 3 subterranean rivers, a barracks (goodge street, I think), disused tube stations, old cellars, plague pits, cholera pits, you name it.
This fact came from a geography professor I spoke with once: many smaller city centre green spots are old plague or cholera pits. Obviously not the really old, established public parks but smaller areas that otherwise, especially in areas like London, and more increasingly Manchester, Birmingham etc. would be built on but haven't been. It's because of what is underneath....wooooo