Hella Jongerius, "Knot Beads Curtain" for the North Delegates Lounge at the United Nations, Manhattan, NY, 2013
Oscar Niemeyer (15 December 1907 – 5 December 2012) with Wallace K. Harrison and Le Corbusier, United Nations Headquarters Pictured with UN Secretary-General Dag Hammarskjöld, c. 1947-52
RIP Oscar.
Whether or not you think that governmental organizations actually accomplish anything concrete, UNESCO has at least created a fascinating list of historical monuments of design. Out of all UN-related subgroups, they just might be the most internationally successful.