The London Underground is the world’s first underground subway. It opened in 1863, which means it’s been around for a whopping 154 years! Originally called the Metropolitan Railway, over time, it has gathered many other nicknames. But one in particular has stuck with Londoners since around 1890 – ‘The Twopenny Tube’. As years went on, this was inevitably shortened to 'The Tube'. It is clear where this came from – the architecture and design of the whole system, including the trains, resembled tubes and pipes. We’ve chosen 20 images which and showcase why this nickname stuck so easily and exemplify the mechanical beauty of the network.