The Great Assembly Hall (321 sq. m. of floor space) is the largest and grandest room in the castle. Its décor and artwork were designed by outstanding artists of the second half of the 18th century - Domenico Merlini and Jan Christian Kamsetzer. The hall was reconstructed based on photographs dating from before 1939, and it contains preserved elements of the stucco work, the rescued statues of Apollo and Minerva by André Le Brun and a sculptural composition depicting an allegory of Justice and Peace. The huge ceiling painting by Marcello Bacciarelli is a reconstruction. The room is decorated with golden stucco columns arranged around the room, magnificent candelabra, chandeliers and gilded wall decorations. During the reign of King Stanislaus Augustus, the Great Assembly Hall was used for court ceremonies, banquets, balls, concerts and theatrical performances.