Madrid traded 10km of 'choking' traffic for a riverside oasis—and changed city life forever.

Madrid started burying nearly 10 kilometres of its M-30 ring road on 24 September 2004 to reduce traffic and noise. By 2011, the city finished a 120-hectare riverside park called Madrid Río above the tunnels. This project reconnected neighbourhoods that were long separated by the busy urban motorway traffic.