In an effort to reduce street traffic, London opened the Metropolitan Railway, the world’s first underground line, in 1863. Its origins can be traced back two decades to the construction of the world’s first under-river tunnel beneath the Thames, which quickly became popular with pedestrians and a major tourist attraction.

Initially, the London Underground was made up of tracks dug slightly below the surface and then covered over. However, as technology advanced and trains transitioned from steam to electric power, the lines became deeper. The ground beneath Londoners’ feet now hums with an extensive network of tube lines that ferry people around the city quickly, efficiently, and out of sight. According to Bradley Garrett, a cultural geographer at University College Dublin and author of Subterranean London, putting infrastructure underground has a lot of appeal. He goes on to say that humans prefer things to be running in the background. It creates the appearance of seamlessness. It almost has a magical quality to it. Along with trains, powerlines, pipes, cables, and sewers, some people have long wished to bury another piece of infrastructure: roads.

No one, not even Musk, has proposed burying all of the world’s roads. But what if we did relocate them all beneath the surface? In an era of increasing urbanization, rising inequality, and climate change, imagining the impact of this raises important questions about how our global transportation system is evolving – and prompts us to consider where we really want it to go.