It took 5 years to transform the 1901 Mediodia electrical power plant across the Paseo del Prado from the Real Jardín Botánico into a dynamo for contemporary art. Pritzer Prize winners Jacques Herzog and Pierre de Meuron managed to multiply the floor space fivefold while creating a brick structure that seems to levitate (it’s actually cantilevered) above its plaza. The building is so strange that you might not immediately notice the 24-meter-high (79-ft.) Jardin Vertical—a wall covered with 250 species of plants that flourish without soil. The interior of the building is equally amazing. The floors are hung on the spine of a winding central staircase that widens as it rises (a trick achieved with rubber molds). Although La Caixa has permanent collections, it is known for its constantly changing exhibitions of contemporary art. Usually three major exhibitions are on display at any given time. Some of the strongest shows are large-format photography, often featuring leading Spanish photographers such as José Manuel Ballester. Many exhibitions are accompanied by lectures, concerts, panel discussions, or other public events.