As its name suggests (XXI = 21), this building is dedicated to contemporary art, represented by both big conceptual, cross-genre exhibitions (think food and its sociocultural consequences, artificial intelligence and the like) or smaller artist-dedicated shows. Highly recognisable Zaha Hadid (1998 - 2009, along with Patrick Schumacher) managed to create here a wonderfully naturally-lit, free-flowing space with diverse volumes to host all kinds and sizes of shows and functions. Gallery café de rigeur.