A room on the plan of a circle, with four niches featuring a concha-shaped vaulting; the niches contain busts sculpted by André Le Brun depicting King’s niece – Konstancja Tyszkiewiczowa née Poniatowska, Maria Józefina Amalia Potocka née Mniszech, Jan Szembek, and Karol Susson. The walls of the Boudoir are decorated with a lightly outlined grill imitating the interior of a garden arbour painted with pastel colours, with flower garlands under the cornice. The decoration was recreated based on historical traces discovered in the mid-1990s.
Placed in the middle – on a round, gilded table with a marble counter, standing on four slim legs – is a room fountain, where scented water was poured in the past. It takes the form of a round, ancient temple and is made of dark-green marble (late 18th century). The furniture is complemented with Neo-Rococo chairs upholstered in green silk.