The complex of King Gia Long's mausoleum is located at Dinh Mon Hamlet, Huong Tho Commune, Hue City. It is the resting place for King Gia Long and his two queens, together with several other members of the royal family. The complex was built during the period from the 18th to the beginning of the 19th century. The two high-ranking mandarins Tong Phuc Luong and Pham Nhu Dang with the help of the well known feng shui master Le Duy Thanh (son of the famous Vietnamese scholar Le Quy Don) were entrusted with the task to seek an auspicious location for the construction.    
In the neighbourhood of the selected location there were 42 mountains looming to support the feng shui terrain of the mausoleum, each with its own name. King Gia Long himself examined and made his decision on the location as well as supervised the  progress of the construction. It was the feng shui master Le Duy Thanh that determined this location, the place where the auspicious energy from the surounding mountains and hills were concentrated to give the mausoleum durable blessing influence for a long time to come. 
The ingenious and harmonious combination of the  fantastic natural landscape with the typical features of the mausoleums of the Nguyen Court gave the Gia Long mausoleum not only favourable elements of feng shui but also impressive and romantic sights.  
Thien Tho mausoleum is the mausoleum of King Gia Long (decease date: Frebruary 1820) and Queen Thua Thien Cao (decease year: 1814). The construction was first started in 1814 and then restarted later from 1820-1833.
Thien Tho mausoleum is the biggest, and boasts the highest architectural artistic values among the ensemble of tombs at Dinh Mon village. This constructioon includes numerous architectural works, small or big, consitsting of  three zones laid out in horizontal line the axles of which all face South. The three zones are:
The burial zone is laid out on a hill called Chanh Trung Son, while the stele zone laid out on Thanh Son hill [Blue hill] , and the worship zone on Bach Son hill [White hill]. As feng shui study stipulates that the east is characterized by the blue colour, while the West is characterized by the white colour; therefore, the two mountains are chosen to represent the elements the blue dragon on the left and the white tiger on the right , both facing in and greeting the two tombs. The mountain stands right in the front of the burial zone is named Thien Tho Son and is regarded as the front protective screen for the mausoleum. ; The Long lake that flows from the left to the right in front of all the three zones is the anteior energy-gathering Space for the whole three zones. All the banks of the lake are paved with big-sized bricks and stone.   
The burial zone is surrounded  by the Holy Rampart wall, inside there are two tombs built of Thanh stone  where King Gia Long (The To Cao Hoang De) and his queen, Thua Thien Cao Hoang Hau, are buried. These two open-air tombs are almost of the same size and are only 24cm apart from each other; They are laid in accordance to the traditional stipulation Male on the left and female on the right. In front of each of these two stone tombs [referred as stone houses] there is a big offering counter made of Thanh stone, which is shaped like a formal wooden bed. The tombs also share the same front and back protective screens, both built with bricks and plaster and decorated quite simply. 
The tombs are surrounded by two layers of wall, the inner of which is rectangular in shape with the back part raised higher, in curving form, apparently meant to hug in all the zone so as to protect it from any landslide from the hillside. The floor inside the Holy Rampart was lined with Thanh stone. In front of the gate in the Holy Rampart stand two bronze unicorns; next is a staircase built in Thanh stone, consitsting of eight steps, and both sides decorated with two undulating dragons portrayed in lime plaster. Further down are six levels of courtyard fringed on both sides with low parapets.   
Each of these levels of courtyard are linked to the next by a three-step staircase both sides lined with dragons or giao long [jiao long: legendary monster living in the depths of the sea] in undulating shape. The lowest staircase, however,  has 7 steps instead of three. Next is the Courtyard paved with Bat Trang tiles which is 49m wide. On both sides of this yard are laid two lines of stone statues (2 elephants, 2 horses), with their saddles and reigns, made of Thanh stone and 10 statues of civil and military mandarins sculpted in sand stone. At the end of the courtyard is the landing stage on bank of the Long lake. The stelae zone is designed quite simply. The house for the stelae is a square pavilion in the traditional style  with a double roof. The pavilion stands on a high base. The stelae pavilion houses a stone stelae with the epitaph written by King Minh Mang to praise his father's merits. The epitaph is delicately carved.  
While the materials for most of the construction in the burial zone and the stele zone are stone, bricks and lime plaster, the main material for the worship zone is wood. The Formal Gate is the main gate for this area. In the center is the Minh Thanh temple for the worship of King Gia Long and his queen, Thua Thien Cao Hoang Hau. In front of this temple are the two subordinate worship pavilions, Tả Vu and Hữu Vu. 
Minh Thanh Temple, the most significant construction in the worship zone, is a double house built in the style two houses combined on the same floor. In the central compartment of the house is laid the altar case, in which there are the tablets with the inscription of the posthumous names of the king, The To Cao Hoang De, anh his queen, Thua Thien Cao Hoang Hau. Formerly, in this temple there were a lot of ritual articles: the offering counter with delicate decorative carvings, the holy set of cranes standing on tortoise pedestals, the set of five worship articles [often including the incense bronze urn, two candlesticks, and a pair of bronze cranes], tall candeliers, urns, flower vases..; the king's utensils such as brush and ink stand, a reading counter, a supporting stand for a washing basin, a tea set, a betel nut casket, a personal charcoal heater, a charcoal heater with handles..all arranged on a wooden bed covered with an ornate mat. On both sides are mirrors posted upright on stands, crystal lamps and ceramic articles purchased from foreign countries. Especially King Minh Mang once kept here for worship the combat helmet, the suit of armour, the saddle together with the guns and swords which King Gia Long had used when fighting the enemy on the battlefield. It is a pity these valuable articles are no more today.           
In front of Minh Thanh temple there is its minh duong [energy-gathering Space] which is a half-moon lake formed from the Long lake. An artificial island is built in the center of this lake, called hòn Trấn [Suppressing rock], rising over the water surface, which helps create chi huyen thuy element [zig zag form of currents to prevent energy from dissipation] in feng shui. At the back of the temple lies a large garden with a Subordinate Worship Pavilion built in the traditional style of three compartments and 2 lean-to's. This house has a simple structure with a plain pattern of supporting frame. The back and the  two left and right sides of the house, as well as the front side of the lean-to's are designed to have brick and plaster walls to increase the  strength of the house.    
Among the seven burial architectural complexes of the Nguyen Court's kings, King Gia Long's mausoleum is one of the greatest fame. As the first to be built, it became the  planning and architectural norms for the ones to be built later. However, now after more than two centuries since the time it was built, the mausoleum was seriously damaged. From 1975 when the nation was unified until 1995, though this historical relic benefited  a lot from the care and efforts of the government and organizations for its preservation, the complex was still in an alarm condition with the risk to become mere ruins in the forests. In the face of such situation, the Hue Monuments Conservation Centre carried out its project to renovate the temple (1995-1996); Investments were put in  for the infrastructure: construction of roads, power lines,  dredging of local water courses in connection with the Perfume river, restoring the Western and Eastern Pavilions (2003); and carryin out a comprehensive archiological survey (2005). 
Restoring the complex of courtyard with the stone statues, the tombs of the king and his queen, the protective walls, the stele zone and the stupas (2009). The restoration was also carried out for the Thien Tho Huu mausoleum and the Gia Thanh temple( including the tomb and worship temple for Thuan Thien Cao Hoang Hau, King Gia Long's second wife (also King Minh Mang's mother), and several other mausoleums located in the neighborhood. 
These different stages of restoration and enhancement step by step helped solve the situation of neglect and damage and gradually brought the complex back to its original beauty. Especially, in the beginning of the year 2015, the construction of the nice bridge Huu Trach, the year-long dream of Huong Tho commune's  people, really gave better chance for tourists to visit the first king of the Nguyen Court's well known mausoleum.