This is a Union Pacific building in downtown Denver. I don't know anything about this building. It's not far from Union Station so presumably it wasn't a depot.
Deep under the streets of London and its snarl of urban traffic is a virtually unknown railway that for 75 years was an artery in Britain’s postal network. Seventy feet below ground, the Post Office railway (more commonly known as the Mail Rail), carried post from Paddington to London sorting offices from 1923 until it was finally abandoned in 2003 due to changing technology.