It is like a spectacular magic trick – making a busy highway disappear while recovering a river whose biodiversity and flow was damaged by nine small dams built in the 1950s and polluted by runoff from the highway. Now bird songs have replaced the roar of traffic on the six-lane M30, the area’s fauna has recovered, and Madrid’s residents can visit a huge leisure and cultural spot,

Conservative politician Alberto Ruíz Gallardón pledged to bury the M30 ring road as part of his bid to become Madrid mayor in 2003. While many people were unhappy with the disruption as engineers tunnelled to reroute the M-30’s traffic deep underground, the €4 billion transformation was ahead of its time and has helped prepare Madrid for the effects of climate change.