In 1774, the Nieborów estate became the property of Michał Hieronim Radziwiłł, swordsman of the Grand Duchy of Lithuania, and his wife Helena née Przeździecka. In 1780, the village of Łupia (later Arkadia) was incorporated into the Nieborów estate. The new owners added new elements to the Nieborów garden and transformed its eastern part into a landscape layout in keeping with the spirit of the age. In
Helena Radziwiłłowa established the Sentimental Garden in Arkadia. Work on its decoration continued until her death in 1821.
The Nieborów estate remained the Radziwiłłs' property until January 1945, when a branch of the National Museum in Warsaw was established on the grounds of the palace and garden complex in Nieborów and the Arkadia garden. The Museum also received part of the farmland, including meadows and pastures, surrounding the Nieborów residence from the east and south.
The entire layout has been the subject of ongoing conservation care since the 1950s. In the post war years extensive conservation work was carried out here under the direction of Professor Gerard Ciołek, later carried out by the State Enterprise for the Maintenance of Monuments. The individual elements of the layout have been well preserved thanks to the constant and meticulous restoration work carried out by the team of the National Museum in Warsaw and its branch, the Museum in Nieborów and Arkadia. The condition of individual buildings and architectural structures and gardens, although requiring further systematic conservation intervention, is satisfactory.