The Riyadh Metro is just the kind of epic, technically mind-boggling undertaking that makes its lead contractor, Bechtel, perhaps the world’s leading builder of one-of-a-kind megaprojects. A Bechtel-led team is installing 39 miles of tunnels, viaducts, deep-underground stations, and soaring terminals, all in the heart of a city that has never seen a bit of commuter track. (Other contractors are building additional metro lines, but Bechtel is doing the most difficult work in Riyadh’s center and using four of the seven TBMs assigned to the project.) At $10.1 billion, the Riyadh job is the biggest lump-sum civil engineering project ever awarded to a single team, and it’s being done for a fixed price. The consortium headed by Bechtel—its partners are contractors CCC of Greece and Almabani of Saudi Arabia, as well as Siemens of Germany, which is supplying the trains—is shouldering all the financial risk. Bechtel has guaranteed that by October 2018, the colossal jumble of parts will be united into a seamless network, with futuristic, self-driving trains running end to end.