London Heathrow
It happens; you miss your flight connection and you have the choice: spending too much money on a (half) night in a depressing airport hotel or over night with your head on your backpack on a back breaking plastic airport seat. Sleeping wasn't really succesfull, so I wandered around in deserted London Heathrow, which is quite scary. But it doesn't happen every day to see usually over crowded places so deserted.