The city of Madrid has transformed its core with a new riverfront park, on land reclaimed from a busy freeway. As noted in the NYT blog Dot Earth, Madrid has joined other cities that are replacing concrete with greenery. A recent NYT article by Michael Kimmelman compares the plan to initiatives elsewhere, including in New York.
Watch a video by the city about the ambitious project, which included a design contest for schoolchildren, the creation of a beach, and the addition of 25,000 trees: