The Madrid Río project was completed on 15 April 2011. It consisted in upgrading the M-30 orbital motorway and running it underground along the Manzanares River, which has been the biggest ecological rebalancing operation in Madrid’s recent history. Where there once used to be thousands of cars on the road, there is now a 10 km long park, a green corridor that stretches from El Pardo to Getafe, joining up the dots that were the previously unconnected woods, green spaces, historical gardens and urban parks, thus providing Madrid with an environmental infrastructure that is one of a kind among large metropolises.