ENThe article presents the case of the Radziwiłł family castles and fortresses and introduces the study of the symbolical meaning of the magnates fortified residences in the Grand Duchy of Lithuania and the Polish-Lithuanian Commonwealth in the 16th–17th centuries. This period is marked by the loss of royal power, as well as the rise of the political influence of limited circle of the magnates families that concentrated large material resources in their hands. This lead to the rise of construction of the private fortresses which started to play significant role in the defensive system of the realm. However the protection of the lord, his family, his subjects and property wasn’t the only function of these fortresses. No less important was the representative function, as fortified residence symbolized the power and influence of its owner. Tremendous importance this aspect gained for the estate society in the early modern Grand Duchy of Lithuania. Sometimes this role was primary and extremely influenced the architectural forms.This aspect is important for the study of the defensive architecture in the Grand Duchy of Lithuania and for the understanding of the architectural specifics of the different castles and fortresses. The Radziwiłłs were one of the most powerful aristocratic families in the Grand Duchy of Lithuania, which explains why they owned so many castles and fortresses (Niasvizh, Biržai, Slutsk etc.). The well-preserved Radziwiłł Archives make this family heritage very promising case for the study of the private castles construction. In addition the representatives of this family had close ties with the Western European, and especially German elites, which is important issue for the understanding of the fortified residences symbolism. This could be explained by the strong influence of the Western European patterns both for the socio-political and cultural development of the Grand Duchy of Lithuania.