Meetings of foreign leaders, even in ancient times, do not just involve two people sitting down to talk. Rather, they are accompanied by a vast network of ambassadors, consuls, aides, translators, etc. All these people need a place to work. In Washington D.C., a stretch of Massachusetts Avenue serves as just this sort of place devoted to diplomacy. Lining this street, are sometimes luxurious, sometimes modest, sometimes old and sometimes brand-new buildings sporting the flags of multiple nations. Most nations have such neighborhoods: Seoul’s Itaewon, Beijing’s Chaoyang, Paris’s 7th arrondissement, Abuja’s Independence and Constitution Aves, are just some examples. These are places where foreign leaders come, discuss, and have their representatives. And not just foreigners: diplomatic quarters are also centers for universities’ international schools, think-tanks and lobbying firms, places to eat, drink and entertain… and spy and counterspy.