The CaixaForum Madrid is a museum and cultural center in Paseo del Prado 36, Madrid, by the Swiss architects Herzog & de Meuron, built between 2001 and 2007, is an example of both green architecture and recycling. The main structure is an abandoned brick electric power station, with new floors constructed on top. The new floors are encased in oxidized cast iron, which has a rusty red color as the brick of the old power station below it. The building next to it features a green wall designed by French botanist Patrick Blanc. The red of the top floors contrast with the plants on the wall, while the green wall harmonizes with the botanical garden next door to the cultural center.