CaixaForum Madrid

Herzog & de Meuron's levitating cultural center near the Prado — a building of weathered, oxidized iron that appears to float above the street, its ground floor seemingly removed, paired with Patrick Blanc's lush vertical garden climbing the wall beside it. The Swiss architects took an old power station and transformed it into one of Madrid's most inventive art spaces. The contrast of rusted metal, living green wall, and floating mass stops passersby in their tracks. For visitors, it offers free, ambitious exhibitions and a piece of world-class contemporary architecture, steps from the city's great museums.