Leeum, Samsung Museum of Art.

Features collection of traditional Korean art, 36 pieces of which have been designated national treasures, and modern and contemporary art from both Korean and foreign artists. Some of the notable names are Alberto Giacometti, Francis Bacon, Andy Warhol, Damien Hirst (yikes!), Jeff Koons, and so on. 

One of the most interesting aspects about this museum is building itself. Three of them were designed by three prestigious architects, Mario Botta, Jean Nouvel, and Rem Koolhaas.