Sieraków Castle, also known as Opaliński Castle, was first built in the 14th century by the Nałęcz aristocratic family. It changed hands several times over the next two centuries, until it came into the possession of the Opaliński family, of whom the castle is often associated. The castle's last owner was the Saxon baron, Piotr Mikołaj Neugarten von Gartenberg. In 1829, due to the construction of a new road in Sieraków, the remains of the castle were pulled down. Only the ground floor of the southern wing survived and was turned into an ice house. In 1991, after the miraculous discovery of the sarcophagi of the Opaliński family in the crypt of Sieraków's Church, it was decided to restore the remains of the castle and turn it into a museum, where visitors could view the Opaliński's coffins.