The term "summer house" was used in Basel to describe the deep vestibules with few exterior windows, which were therefore pleasantly cool in summer. This was also true for this vestibule, through which one entered the private living floor of the Burckhardt family. Already in the staircase, the change from stone to wooden flooring of the steps indicates the transition from the representative bel étage to the private living rooms. The floor has a lower room height than the two lower representative floors, which creates a more intimate atmosphere. From this "antichambre", a sequence of rooms with the bedrooms of the master of the house and his spouse adjoins towards the street

Today, the summer house houses, among other things, various mementos of the legendary Count Cagliostro (1743-1795), who was a guest of the Sarasin-Battier family in the "White House" in the 1780s, where, in addition to his work as a "miracle healer", he also founded a freemason lodge. Also noteworthy as exhibits in the summer house are the lime wood reliefs hanging next to the window, created by the Parisian architect and sculptor Henri-Joseph Aubert Parent (1753-1835) around 1813. Aubert Parent's extremely finely carved still lifes with bird scenes also found favor with the French King Louis XVI (1754-1793).