The oldest city in Vietnam is Hanoi. Hanoi has a rich history dating back over a thousand years and has served as the capital of Vietnam for centuries. It was founded in 1010 during the Ly Dynasty and has since been an important political, cultural, and economic center in the country. Hanoi is known for its well-preserved historical sites, including the Old Quarter, Hoan Kiem Lake, and the Temple of Literature, which showcase its ancient heritage.