Crossrail, London

Many underground railways have been built before, but the logistical manoeuvring that has been necessary to keep a city of millions running above while this new east-west link is threaded through the sewers, cables, and foundations of London – not to mention existing underground tunnels – is truly staggering. Crossrail is strange for the UK, in that much of the infrastructure of the country is old, and there’s not a great deal of opportunity for expansion. But elsewhere in the world, there are projects on site that set new records for size.