Washington Dulles International Airport — Dulles, United States

Opened in 1962 as a purpose-built gateway for the nation's capital, Washington Dulles International Airport, recognized by the code IAD, was sited well outside the city in Virginia to allow room for future growth that the more constrained National Airport closer to downtown could never accommodate. Its main terminal, designed by Finnish-American architect Eero Saarinen, remains an architectural landmark with its distinctive sweeping, catenary-curved roofline suspended between rows of angled columns. For decades passengers were shuttled between terminal and aircraft aboard distinctive mobile lounges, a system since partly replaced by underground trains and connector walkways as the airport modernized. Named for former Secretary of State John Foster Dulles, IAD serves as United Airlines' primary hub for the Washington region and handles much of the area's long-haul international traffic, connecting the capital directly to Europe, Africa, the Middle East, and Asia.