ENThe purpose оf the report is to draw the audience attention to the architectural and decorative features of Renaissance Siesikai estate castle (Ukmergė district), which hasn't been studied yet. Also Hie report strives to research the historical circumstances of the castle construction, which were determined by the castle builder Gabrielius Daumantas Siesickis (1517) biography and his serving in the estate of the king Vladislovas Jogailaitis in Buda. Siesikai estate castle construction is assigned to the period of 1492-1517. Both the architecture of the castle as well as some of its decorative elements, such as arabesque-shaped floor tiles have not only characteristic features of the Adriatic Sea, but also of Baltic decorative elements - the signs taken from calendar and solar system. The wall paintings of Siesikai castle representative premises illustrate the work and holidays calendar of every month, rendered on walls frisc. On the eastern wall of this room there are painted the antique myths allegories, based on miniatures of Ovidijus Metamorphoses painted and, possibly reflecting the family slogan of Siesickiai. Another unique feature of these representative premises is the windows location and orientation according to the parts of the world in such a way that during the winter and summer solstices the sun illuminate the room door and during the spring equinox the sun illuminate certain signs painted on the wall. In the eastern premises of the castle is a small room. It is supposed that this is an Orthodox chapel - tabernacle appointed to the first owner of the castle Orthodox Kotryna Palubinskaitė. Siesikai castle architecture and decoration have the unique Renaissance elements. Therefore there are required deeper and broader researches of art history, art criticism, architecture and archeo-astronomy.