Fodor's Expert Review Palais des Nations

Built between 1929 and 1936 for the League of Nations, this monumental compound became the European office of the United Nations in 1946 and quickly evolved into the largest center for multilateral diplomacy in the world. Today it hosts some 9,000 conferences and 25,000 delegates each year; it is also the largest nexus for United Nations operational activities after New York.

Security is tight: be prepared to show your passport and arrive at least 45 minutes before your scheduled tour. Points of particular interest include the Assembly Hall, the largest of 34 conference rooms, where the UN General Assembly and scores of world leaders have met, and the ornate Council Chamber, home to the Conference on Disarmament, which glows with allegorical murals. Tours last about one hour and are conducted in 15 languages, including English.