Little now remains of the former royal citadel of Thăng Long (Hà Nội). A citadel existed at the site - originally known as Đại La - from at least the 7th century, but not until the 11th century did it become the capital of the Việt. In 1010 Lý Thái Tổ, the founder of the Lý dynasty, removed the court from Hoa Lư in present-day Ninh Bình Province to Đại La, which was subsequently expanded and renamed Thăng Long Citadel. It was to remain the royal capital until 1802, when Nguyễn Ánh took the throne as King Gia Long (1802-1819), transferring the royal seat of government to Huế, downgrading Thăng Long to the status of a provincial capital and changing its name to Thăng Tinh, removing the word 'Long', which was regarded as a royal symbol.

In 1805 the ancient northern citadel was rebuilt according to Vauban principles, on a smaller scale than before, with five gates, none of which faced south. In 1831 Gia Long's son Minh Mạng (1820-1840) once more changed the name of the city, this time to Hà Nội ('city within two rivers') and in 1848 Tự Đức (1847-1883) further reduced its importance by ordering the destruction of most of its royal palaces and the removal of many articles of value to Huế. Following the colonial conquest, the French symbolically took over the citadel, destroying most of the remaining buildings and replacing them with military barracks and depots. Thereafter it served as the headquarters of the People's Army (and latterly of the Ministry of Defence) until 2004, but in that year the Ministry of Defence began transferring the entire 49,135 square kilometre site to the Hà Nội People's Committee with a view to permitting necessary archaeological work and finally opening up most of the citadel to the public as a tourist attraction before the Hà Nội 1,000 celebrations in 2010. Responsibility for managing the site as a visitor attraction has since been passed to the Hà Nội Service of Culture and Information.

At the time of writing visitors entering through the Đoan Môn (main gate) can tour the Điện Kính Thiên (Kính Thiên Palace), the 'D67' war room and underground bunker of General Võ Nguyên Giáp and a number of other areas of the old citadel - with the exception of the Điện Hậu Lâu (Princess's Palace) and the Bắc Môn (north gate), which have their own separate entrances (see addresses above). The citadel flag tower (Cột cờ Hà Nội) can be viewed when visiting the nearby Việt Nam Military History Museum.