Antal Grassalkovich I began the construction of the mansion house immediately after he acquired the property of Gödöllõ. He ordered the design from András Mayerhoffer, a well-known master of Baroque architecture. The construction of the seven-wing building, in the form of a double U, was implemented in several phases.
The first construction phase lasted from 1741 to 1749. In this time the five internal wings of the building were accomplished, with the chapel on the northern side, and the riding hall on the southern one. Each corner of the main frontispiece was then closed in by a tower. The central projection obtained its present form in the second construction period (1752-1759). The sixth and seventh wings were built during the third phase of construction which may have been in the 1760s. On the ground floor of the wing linked to the chapel a bath covered with red marble slabs and decorated by frescoes was made, with direct passage to the greenhouse nearby. On the first floor of this wing and in the wing opposite living rooms were formed.
The specific architectural solutions applied to the mansion house served as models for Hungarian Baroque architecture. The features of this style called the Gödöllõ style could be detected, among other places, in the mansions of Aszód, Hatvan, Nagytétény and Pécel. The most conspicuous of these stylistic features is that the wings connected to the main frontispiece expand not towards the side of the arrival but backwards. Another characteristic of the Gödöllõ style is that the architecturally most emphasized part of the building's main facade, which is divided by the three projections, is the middle projection. The balcony rests on three Icons columns of red marble. On the rococo banister of the balcony, among the military insignia, the arms of the Grassalkovich family can be seen. The six metres high arched windows are bordered with rich ornaments. The splendour of the central projection is enhanced by the double cupola formed above the attic in a broken arc-form.
In this multiply emphasized part of the building is the stateroom which can be reached by two flights of stairs starting from the central driveway in opposite directions. The stairs have decorative stone railings with a basket pattern and tracery. The walls of the stateroom with a basic area of 170 square metres and an internal height of 9.5 metres are decorated with gilded stuccos. Above the entrance a hidden music hall is connected to it.
In a northern and southern direction from the stateroom the less emphasized units of the building follow in chain-like rows. In the period of the Grassalkovichs, the rooms of the family's female members lay to the north, and those of the men southwards. Antal Grassalkovich I had let his own suite of rooms to Maria Theresa when she visited Gödöllõ in 1751. The room transformed for the queen, lined partly with genuine and partly with artificial marble is the most richly decorated room of the mansion house. Opposite its entrance door a full-figure portrait of Maria Theresa preserves the memory of the queen's visit.
The huge park belonging to the mansion house is divided by the building into the Upper and the Lower Garden. The French-style Upper Garden, linked to the internal yard, was famous because of its special plants and the statues of mythological subjects. The Lower Park contained the kitchen garden, the game preserve and the pheasantry.
Even Antal Grassalkovich II made some alterations to the mansion house between 1782 and 1785. He had the corner towers of the main frontispiece pulled down and replaced by projections with knee-roofs which can still be seen. At that time, the house musicians lived in the rooms above the greenhouse and the bath, hence this storey was called the musicians' passage. At the end of the wing opposite this, Grassalkovich II made a theatre with a double dress circle and with excellent stage equipment. (This is the only Baroque theatre in Hungary which remains.) The performances of the troupes of Vienna and Buda were accompanied by the house musicians. From the theatre there was easy access to the beer cellar which was connected to the riding hall, too.
In the time of Antal Grassalkovich III, smaller alterations were made to the building under the direction of the architect József Hild. The orangery was then built onto the last wing of the northern side. At the wish of Leopoldina Eszterházy, the wife of Grassalkovich III, the French Park was transformed in 1817 into an English-style landscape garden. At the same time, in the Lower Park, opposite the mansion house, two swan pools were formed.
In 1841, after Antal Grassalkovich III, the male-branch of the family died out. The estate inherited on the female line was purchased in 1850 by a banker, György Sina, and in 1864 it became the property of a Belgian bank. The owners hardly lived in the house, so that its condition during these two and a half decades deteriorated considerably.
The second golden age of the palace began in 1867 when the Hungarian state bought it back and put it among the crown lands. Based on the design of Miklós Ybl, the building was renewed within half a year and offered as a retreat to Francis Joseph, Emperor of Austria, on the occasion of his coronation as Hungarian king.
In the course of the renovation the positions of the male and female wings were reversed. North of the stateroom came the suite of rooms of Francis Joseph. The first was the smoking room, the second the writing room, whose door, for the purpose of security, had a thick armoured plate built in. The walls were decorated with the king's hunting trophies. In the king's apartment the silk wallpaper was grey while the seats and armchairs were cowered with yellow leather.
On the other side, Queen Elisabeth's set of rooms were in her favourite colour, violet. Later on, following the Schönbrunn model, the wooden panelling was painted white and the draperies changed into red ones. The rooms of Queen Elisabeth were situated south of the stateroom. After the small salon decorated with paintings in oil and small sculptures, came the queen's writing room, and then the dressing room and the bedchamber, which had earlier been designed for Maria Theresa by Antal Grassalkovich I. The spiral staircase behind the bedroom led to the queen's salon on the ground floor. The riding hall could be reached from here through a wooden corridor.
Beyond the rooms of Queen Elisabeth were the rooms of Ida Ferenczy, her lectrice. At the end of the corridor came the apartments of the children, Maria-Valeria, Gisella and Rudolph.
The theatre hall fell victim to the renovation, since it was divided into rooms for the attendants coming with the royal family. At the same time, the greenhouse and the Baroque bath disappeared from the wing opposite the theatre. In their place a pharmacy and guest rooms were established. In the one-time passage of the musicians, the court officers were accommodated. The riding hall which was in a ruined condition was also much altered. As a result of this, even the beer cellar which opened out from here vanished. This was the time when the marble stall was built onto the Baroque stall and, on the opposite side, the new carriage house was accomplished.
The royal family stayed in Gödöllõ mainly in the spring and the autumn. Their presence here was characterized by an atmosphere that was less formal than that in Vienna. The surrounding forests, rich in game, offered excellent opportunities for hunting. These were often pursued by a company of high-born guests, just like the greyhound racing or the riding demonstrations. Queen Elisabeth was a legendary rider, but in Gödöllõ she could also indulge in some other of her passions - for instance in writing verse. The people of Gödöllõ enveloped her with devoted love: they celebrated her name-day with torchlight processions and serenades.
The royal visits bringing festivity into the life of the community became rare after the tragic death of Queen Elisabeth in 1898. The last time Francis Joseph came to Gödöllõ was in 1911.
The first longer visit of his successor, Charles IV, was ended by the decay of the monarchy. The last Hungarian king left Gödöllõ on October 26. With this began a new era in the history of Hungary, too.
At the end of 1918 the Ministry of Finance provided for the custody of the building. In spring 1919 the headquarters of the army of the Hungarian Soviet Republic took up its residence in the mansion house. Aurél Stromfeld, chief of general staff, directed the military operations from here. In August Romanian troops occupied the building, whereupon the robbing of the palace and the estate commenced.
From 1920 on the building became again a residence of the head of state in the administration of the treasury. Miklós Horthy, the governor, often came here to rest and to hunt, and again heads of states and aristocrats were the visitors of the place. In the era of Horthy, apart from the regular maintenance work, no alterations in the buildings were carried out. This was the time when in the southern garden the 170 square metre air-raid shelter was constructed, which could also be approached through an underground corridor leading from the basement of the building.
During World War II the palace was not damaged. In the autumn of 1944, however, German troops almost completely looted it. The Soviet army established a field-hospital in the palace and burnt all the remnants of furnishing that remained in the house.
From 1950 on, Soviet troops were stationed in the outbuildings of the court. In the ends of the northern wings the Ministry of Defence established its basic storehouse. The mansion house itself, which had been declared a monument, served as a social welfare home.
Action for the protection of monuments which started in 1985 was severely hindered by the various functions present in the group of buildings. The palace was left by the Soviet troops in 1990 and emptying it completely took until the end of 1994.
The renovation and utilisation of the palace is co-ordinated by the "Gödöllõi Királyi Kastély Közhasznú Társaság" (Gödöllõ Royal Palace Public Utility Company). According to the plans, a centre for museums and culture is going to find its place here.