Modeled on London's Crystal Palace of the 1850s, Madrid's greatest wrought-iron and glass-domed Industrial Revolution structure was launched just 30 years later to stage an exhibition of Philippine tropical plants. It stands in the heart of the Retiro Park, reflecting charismatically in a small lake inhabited by ducks, grey lag geese, and black swans, and forms one of Madrid's most enduring bucolic images. Exhibitions of modern art, ranging from surrealistic metal sculptures to aviary shows, are regularly held inside the building.