The Citadel of Hanoi, also known as the Imperial Citadel of Thang Long, is a historic site located in the heart of Hanoi, the capital of Vietnam. This UNESCO World Heritage Site dates back to the 11th century and served as the political center of various dynasties in Vietnam. The citadel features ancient architecture, including the Flag Tower and remnants of royal palaces, showcasing the rich history of the region. The citadel covers an area of approximately 18 hectares and is surrounded by walls and moats. It has been a witness to significant events in Vietnamese history, including the struggles against foreign invasions. Today, the Citadel of Hanoi is a popular tourist destination, offering visitors a glimpse into Vietnam's past and its cultural heritage.