The following article is devoted to the study of the interiors at the official residence of K. V. Nesselrode — the Head of the Ministry of Foreign Affairs of the Russian Empire. Attention is drawn to the work of the chief architect K. I. Rossi as the author of the interiors of the state rooms of the residence. In published studies devoted to the work of K. I. Rossi, draw emphasis on the external appearance of the Ministry building, whereas the interior decorum of the state rooms is mentioned only partially. In articles and monographs one can only an overview and generalized dates in relation to the construction of the interiors while objects of decorative and applied arts are completely excluded from the comprehensive study. In-depth research of this topic with reference to unpublished sources makes it possible to clarify the degree of involvement of K. I. Rossi in the development of the interiors decoration, furniture design and creation of other smaller decorative objects for the Ministry’s state rooms. Moreover, the surviving interiors and elements furniture in the eastern wing of the General Staff Building serve as valuable source for the study work of the great architect K. I. Rossi. Extensive study of those sources makes it possible to create a detailed description of the historical appearance of the state rooms at the Ministry of Foreign Affairs. A comprehensive analysis of the preserved architectural evidence allows us to reconstruct the original appearance of the interiors in great detail. K. I. Rossi’s ability to create rich interiors designs for smaller projects with complex planning system while remaining true to his own style is a sign of true artistic genius. © 2025 Saint Petersburg State University. All rights reserved.