The Neue Galerie New York an absolute treasure of a museum, showcasing fine and decorative arts from Austria and Germany, from 1890-1940. The collection's most prized piece is Portrait of Adele Bloch-Bauer I by Gustav Klimt, which was stolen by the Nazis from Adele and her family in Vienna, just before World War II. It was only returned to Adele's family, to her niece Maria Altmann, in the 21st century after a lengthy legal battle. It is one of my favourite portaits in the world, and photos do not do it justice - it has to be experienced in person!
See also: Cafe Sabarsky & Cafe Fledermaus, the museum's two gorgeous, onsite restaurants.
For more on the story of the painting, watch Woman in Gold, starring Helen Mirren and Ryan Reynolds.