- On the surface of 5,2km2, Hue Citadel is situated on the Northern bank of the Perfume River. This construction stared in 1805 under the reign of Emperor Gia Long and completed in 1832 under the reign of Emperor Ming Mang.

- Hue Citadel was built by the combination of Western architecture and Oriental architecture. It has a system of three circles of ramparts, namely from outside to inside: Hue Citadel, Royal Citadel (or Imperial City) and Forbidden Citadel (or Forbidden Purple City).

- The surface inside Hue Citadel is dividing into many small sections with different functions had about 100 buildings with different scales. All constructions were arranged according to a tight and symmetric design. Most of the constructions were symmetric through the main axis such as Flag Tower, Noon Gate, Esplanade of Great Salutation, Thai Hoa Palace, Can Chanh Palace (Emperor’s Official Working Palace), Can Thanh Palace (Emperor’s Residence), Khon Thai Palace (Queen’s Residence), KienTrung Pavilion, and Hoa Binh Gate. The other constructions are designed in front, back, left, right, up and down positions.

- The Citadel, square in shape, is almost 10km in circumference, 6m high, 21m thick and 13 entrances. On the top of the walls that surround it, 24 bastions are established for defensive purposes.

- The Imperial City is located in the center of the Citadel, about 2,450m in circumference. Access to the Imperial City can be made by four entrance gates: Noon Gate (South), Hoa Binh Gate (North), Hien Nhon Gate (East), Chuong Duc Gate (West).

- Noon Gate is the main entrance to the Imperial City and only used for the Emperor. This is the construction remaining relatively intact.

- Forbidden Citadel (Forbidden Purple City)is located inside the Imperial City, is reserved for Emperor and his family, about 1,225m in circumference, including 50 architectural constructions of different sizes and 10 gates for facilities of entrance and exit. It is almost isolated from the outside world.