The ballroom was commissioned by Giuseppe Antonio Arconati and was finished around 1742. An elegantly decorated room in rococo, its key role was to host parties that were held for the delight of guests and owners. It is accessed through a small living room that precedes it, designed to entertain guests waiting to enter the hall itself. The room is a white rectangular one, decorated with interwoven motifs with swirls and arabesques.
Decorations cover the ceiling fully and almost of the walls of the room. The entrance door and French doors are recessed in rectangular spaces and surrounded by stylized motifs that decorate the rest of the room. From the thick gilded stucco, illusionistic scroll motifs proliferate and intertwine between one space and the other, creating oval medallions in black monochrome, surrounded by gilded decorations. In the lower part of the wall is a wainscot/baseboard painted white and pink faux marble, which follows the entire wall of the room, drawing an elegant oblong figure with small scroll motifs. At the shorter side between the two entrance doors, is a new decorative element, a large rectangular frame with mixtilinear scrolls that contain figures outlined in relief. Recognizable as a diamond pattern at the bottom, towards the end of the frame, these geometric shapes tend to flatten more and more until they become square. These forms are characterised by a stucco relief profile and four small golden decorations in the centre, and compose a small golden square inside the diamond. In the upper part of the hall runs a golden contour that accompanies the triumph of rococo decorations on the ceiling: a profusion of light and elegance outlined in gold makes it almost impossible for the visitor to distinguish what is real and what is just painted. Looking closer, one can see three dimensional roses and leaves in brass that trace these refined compositions. At the centre of a ceiling is a mixtilinear medallion surrounded by two symmetrical decorative figures in pale pink.