D EEP IN THE ground beneath the western Paris business district, the din is bone-jangling. With compact mechanical diggers, workers are excavating rubble from 22-metre (72-feet) shafts. These will take 60 supporting pillars for a vast new train station, to be buried 35 metres underground. Welcome to one of Europe’s biggest infrastructure projects: an ambitious scheme to encircle Paris with a new metro loop, and shift the way people think and move about the capital.

The new station at La Défense, built as part of the westward extension of the E line, will link up to a huge looping network known as the “Grand Paris Express”. Most of the French capital’s existing rail and metro lines are there to carry people in and out of the city centre. The new underground loops, by contrast, focus on moving them around the suburbs.

One loop will run from Charles de Gaulle airport in the north, via the banlieue of Seine-Saint-Denis, westward to the skyscrapers of La Défense, and on in a ring around southern and eastern Paris, outside the capital’s périphérique ring road. A second loop will link the first to Orly airport in the southern suburbs, and then west via the Saclay university cluster at Palaiseau to Versailles. When complete, the new driverless underground network will feature 68 new stations and cover 200km, nearly twice the length of London’s new Crossrail.