Five years later, Gustav made the property his own. About ten years after that he also acquired the neighbouring property of Brahelund, thereby giving Haga more or less the boundaries it has today.
During his early years at Haga, Gustav III stayed in what is now the old corps de logis, still to be seen in the southern part of the park.
Meandering paths, sudden vistas, and radically tamed scenery alternating with the grandeur of unspoiled nature are typical components of this landscaping.
A park of this kind also had to include a number and variety of buildings and pavilions, such as the Turkish Pavilion, which still survives at Old Haga.
In its grandly designed galleries, he wanted to display his great collection of antique Roman statues (now to be seen in Gustav III's Museum of Antiquities at the Royal Palace of Stockholm).
The "Museum Palace" at Haga was designed by the French architect and stage designer Louis Jean Desprez.
The corps de logis of the Brahelund estate, overlooking the shore of Brunnsviken, was rebuilt as Gustav had intended and became Gustav III's Pavilion at Haga.
The interior was decorated by Louis Masreliez in Pompeian style. Masreliez had studied for several years in Italy and was closely familiar with Roman antiquity.
Not only are the permanent fittings and decorations of the different rooms very well preserved, but also a great deal of the pavilion's original furniture is still in situ.
Internationally as well, Gustav III's Pavilion at Haga is one of the finest examples of European Neo-Classicism.