The architectural designs by Carlo Fontana were cretaed for Central European aristocrats in the framework of "baroque" culture including high knowledge of architecture among the aristocratic patrons. The article deals with the involvement of Count Martinitz in the design process of his palace in Prague as well as with its context. The diplomatic mission of Martinitz, the Imperial ambassador in Rome, serve to his social promotion as well to establishing of contacts to the Italian society which were used even after his return to Prague.