The most historically important site in Rydzyna is Rydzyna Castle, formerly the residence of king Stanisław I and the Sułkowski princes. The castle in Rydzyna was built at the beginning of 15th century by Jan of Czernina. At the end of the 17th century, Italian architects Joseph Simon Bellotti and Pompeo Ferrari erected the present Baroque castle on its ancient foundations. The first owners of the castle were the Leszczyński family. Together with its park and surrounding areas, it was one of the most splendid palaces in Poland. Between 1704 and 1709 it was a residence of the Polish king Stanisław I. In 1709, during the Great Northern War, the castle was partly burnt by the tsar's soldiers. However, wall-paintings and stucco works in representative rooms, made by the best Italian artists, were not destroyed completely, and the castle was restored and expanded by Prince August Sułkowski, who purchased the Leszczyński estates in 1738. The castle, together with its adjacent park and the surrounding terrain, forms one of the most valuable castle-park complexes in Poland
Today, it can be visited as a hotel and restaurant.