This building was once the residence of the kings and the seat of the Republic of the Two Nations. Today it serves as a museum and as a centre of education, culture and art. It is freely accessible to the public and is the venue for important state ceremonies. Together with a complex of the Old Town, it is on the World Heritage list.

The Royal Castle was reconstructed in the years 1971-1984 thanks to the generosity of the population and Poles living abroad.

The work involved the reconstruction of fragments, masonry, stucco, wood carvings and wall paintings. In the course of the work, several works by important artists were found: paintings by Bernardo Bellotto, known as Canaletto, Marcello Bacciarelli and John Pferch. Sculptures by André Le Run, Giacomo Monaldi and Phillipe Caffieriego. French furniture from the late eighteenth century. The exhibition is today enriched by gifts from the Polish state, foreign gifts and works from private collections.