The project critically analyses the role of the Castle in the political, social, and cultural context of the interwar Czechoslovakia. Unlike the existing historiographic interpretation frameworks, which overlook its role as a centre of ideology, the project treats the Castle as a personified public individual, represented mainly by T. G. Masaryk, who is also the leading author of the ideological content of its activity. The project works with the concept of Masaryk and the Castle group as the centre of a new democratic society. From this position, fearing for the stability of a new state, they were trying to build the citizens’ trust in the new system and complete the transformation from the imperial to the republican era. Slovakia constituted a special case, where the response to the Castle was strongly influenced by autonomist discourse and criticism of centralisation. The project also follows possible parallels with the situation in neighbouring countries, especially Poland, and the subject of the Castle’s perception abroad.