Despite the monumental changes in history and the destruction of many structures, the ancient Thang Long Imperial Citadel still retains some grand architecture. 

The citadel was built along a north-south axis, with its main gate facing south. The central axis was known as the “divine path” or “imperial path” (the king’s path).

Entering from the south, the first architectural item is the Ky dai, commonly known as the Hanoi Flag Tower. This marks the southern beginning of the central axis of the citadel.

The Ky dai was built during the Nguyen Dynasty, consisting of three base levels and a column. It served both as a flagpole and an observation tower. The tower is impressive in scale, standing 33.4m high, or 41.4m, including the flagstaff.

From here, following the “imperial path”, it would reach Doan Mon. Doan Mon, or the Southern Gate, is another grand structure featuring five large gates.

At the heart of the Thang Long Imperial Citadel was Kinh Thien Palace – the venue for court meetings and where the emperor welcomed high-ranking scholars and foreign envoys. This was the most important centre of power in Dại Viet for centuries. Kinh Thien Palace no longer exists, but the stone steps with a pair of dragons, crafted during the Early Le Dynasty, have been preserved intact.

The final major surviving item of the ancient citadel is the Cua Bac (Northern Gate), located on Phan Dinh Phung Street. This large gate faces north. On its walls, there are still marks of two cannon shots fired by French colonial forces during their attack on Hanoi in the late 19th century.

In addition to the feudal architectural features, the Thang Long Imperial Citadel also preserves many French architectural works and structures built during the resistance against the US. Among the most notable is the D67 House and Bunker. The full name of D67 is the Politburo and Central Military Commission Meeting Room. 

Due to heavy American bombing, the Ministry of Defence decided to build the D67 House and Bunker to ensure the safety of the headquarters during the war.

The D67 House and Bunker relic features the Meeting Room of the Politburo and the Central Military Commission, the Office of General Vo Nguyen Giap, and the Office of General Van Tien Dung. The building is connected to a 9m deep bunker, solidly built to withstand bombs. The bunker has three floors. Here, the Politburo and the Central Military Commission made many important decisions, including meetings to decide on the historic Ho Chi Minh Campaign in the spring of 1975, completely liberating the south and unifying the country.

The place where the royal court was held is the most important space in the Thang Long Imperial Citadel. During different periods of time, the court had different names such as Can Nguyen Palace and Thien An Palace. During the early Le Dynasty and then the Mac Dynasty, and the Later Le Dynasty, the court location remained unchanged and was called Kinh Thien Palace. When the Nguyen Dynasty relocated the capital in Hue, Kinh Thien Palace was destroyed and replaced by Long Thien Palace. The French then destroyed Long Thien Palace to build the Artillery Command Headquarters right on the foundation of Kinh Thien Palace.

As the Ly and Tran Dynasties were too long ago, scientists wanted to decipher the mystery of the architecture of Kinh Thien Palace during the Le Dynasty. The great difficulty is that the building was destroyed two centuries ago.

Excavations have helped to gradually reveal the appearance of Kinh Thien Palace. In Oriental architecture, and Vietnam in particular, the pillars play the main role of the construction. The construction workers made the pillar foundations and placed stone blocks at the foot of the pillars. The 2023 archaeological excavation created a turning point as it unveiled ten single foundations and seven double foundations, which translates to a total of 24 single foundation units on the foundation of Kinh Thien Palace.

Based on the findings, scientists initially determined that Kinh Thien Palace had a scale of nine compartments, with the middle compartment measuring 6.8m wide, the side compartments 5.35m wide, and the two end compartments 3.4m wide each. The total area of Kinh Thien Palace during the Le Trung Hung period is estimated to be about 1,485 sq.m.

Based on the findings, scientists initially determined that Kinh Thien Palace had a scale of nine compartments, with the middle compartment measuring 6.8m wide, the side compartments 5.35m wide, and the two end compartments 3.4m wide each. The total area of Kinh Thien Palace during the Le Trung Hung period is estimated to be about 1,485 sq.m.

Along with the foundation, the scale, roof and the roof-supporting frame of Kinh Thien Palace are very remarkable. While religious and belief structures often use fish-scale tiles and unpolished terracotta-coloured tiles, the tiles in Kinh Thien Palace are yellow-glazed tube tiles (the yellow colour was associated with the emperor). Each tile on the eaves is in the shape of a dragon's head, the next tiles are the dragon's body, and the roof tile is the dragon's tail. The entire set of tiles is a flock of lively dragons.

Regarding roof support, the most important milestone was in 2017-2018, when scientists found 70 wooden roof structures. Many of them are in the structure of the "dougong" system. In 2021, in the east of Kinh Thien Palace, an architectural model was also found that truly reflects the wooden frame supporting the roof, which is the "dougong" system — a structural element of interlocking wooden brackets, located under the porch and roof, which expands the porch area, has the ability to withstand force, and plays a decorative role to create beauty for the building.

Dr. Bui Minh Tri, Institute of Imperial Citadel Studies, Vietnam Academy of Social Sciences, who directly researched the frame and roof of Kinh Thien Palace, said: “Although the complete "dougong" system has not been found, combining archaeological documents, based on the architectural form of the palace painted on pottery and architectural model documents of the Le so Dynasty, the Institute of Imperial Citadel Studies has enough basis to firmly determine that the architecture of Kinh Thien Palace belongs to the form of "dougong". This is an important discovery, the key to research to decode the mystery of the architectural form of Kinh Thien Palace.” 

Visiting Thang Long Imperial Citadel today, visitors find it difficult to imagine and feel the architectural beauty and understand the message of the ancients, because most of the works are only ruins. Therefore, Professor Nguyen Quang Ngoc as well as many other scientists emphasised that, with the special significance of Kinh Thien Palace, the restoration is the responsibility of the government and scientists to the people, and to history. This is a task that needs to be focused on in the coming time.

Thang Long Imperial Citadel is the most important heritage of the Capital, and at the same time is one of the attractive tourist destinations. Every year, Thang Long Imperial Citadel welcomes hundreds of thousands of domestic and international tourists.

One of the site's most attractive tours is the night tour "Decoding Thang Long Imperial Citadel".

The night tour "Decoding Thang Long Imperial Citadel" lasts about 90 minutes and starts from Doan Mon — the main gate to the Forbidden City, residence and workplace of the ancient king.

Joining the tour, visitors can experience the ancient Imperial Citadel space, admire valuable artifacts and antiques found at Thang Long Imperial Citadel in the exhibition house with the theme "Thang Long - Hanoi - A thousand years of history from underground", and offer incense to commemorate the ancestors at the Kinh Thien Palace threshold area.

The final destination of the tour is the Archaeological Site at No.18 Hoang Dieu Street. After years of excavation, archaeologists have discovered millions of artifacts, layered over one another, spanning 1,300 years. The tour concludes with a game called "Decoding the Thang Long Imperial Citadel", open to all visitors.