Designed by Herzon & de Meuron, the CaixaForum is the museum and exhibition space of the La Caixa Foundation (think savings banks). Inside is an impressive collection of post-1980s artists, but the building itself is the biggest attraction. An example of industrial architecture, it has a staircase that could rival a Gaudi and a vertical garden by Patrick Blanc with 15,000 plants from 350 species.
CaixaForum Madrid, Paseo del Prado, Madrid, Spain