Located in the main axis, Ngo Mon heads to the South. The U-shaped construction has its bottom located in the Citadel and two wings reached out. The main gate is divided into two parts i.e. foundation and Ngu Phung pavilion (the pavilion of five Phoenixes).
Its foundation is nearly 5m high. Its 57,77m long bottom is considered as the continuous part of the Citadel. The two wings are 27,06m long. Its U-shape not only makes the construction become more majestic, but also facilitates safe guards.
The thick and high foundation was designed in "thuong thu ha thach" (the distance between 2 columns is smaller at the top part and larger at the lower part, like spreading legs) style which created a majestic look. There are three parallel entrances constructed at the middle of the foundation. Only the Emperor was allowed to enter the Noon Gate. Civil and military mandarins entered the other two entrances which are on the left and right sides of the Ngo Mon and respectively called the left gate and the right gate. Inside the structure, there are two more ways called Ta dich gate and Huu dich gate. These are designed for servants, soldiers, elephants and horses serving the royal procession. The upper parts of these 5 gates are arch-shaped. Particularly, the two ends of the three middle gates are supported by horizon and vertical beams. These beams are covered with a thin layer of bronze for aesthetic purpose.
The construction is mainly made from wooden-hammer brick and stone. There are two stone staircases constructed on two sides. Around the foundation is the railing system decorated by many kinds of ceramic glazed hollow blocks.
The two-storey pavilion called Ngu Phung (the pavilion of five Phoenixes) was designed in U-shape with 13 compartments. In spite of sharing the same frame made from Lim wood, the upper part is divided into 9 separated roofs coming in different sizes and heights. This undulating feature may explain why the construction was named "the pavilion of five Phoenixes". It is roofed with yellow and green ceramic glazed tiles and laid in Yin-Yang style.
The pavilion of five Phoenixes consists of 100 pillars. Of all, there are 48 shared-pillars. The lower floor is left empty except for the middle building in which mirror door system is placed in the front. Also, wall-like structure is set up on its back where the Emperor sits while attending ceremonies. On the upper floor, louver doors are placed on the front of the middle compartment. Windows which come in all shapes such as circular, fan, bronze chimes ect were built around.
The decoration of the Ngo Mon is particularly concerned. It was roofed by ceramic glazed tiles and decorated with many featured patterns such as stylized bat, butterfly and dragon are made from colored ceramic pieces. Artisans specially concerned about decorating wooden railing.
For its special historical values, the Ngo Mon was among hundreds of relics within Nguyen dynasty monuments complex recognized as world Cultural Heritage by UNESCO in 1993.