The New Castle was built in the 1730s-1740s as a residence for the Saxon kings of Poland, Augustus II and Augustus III, who used Hrodna as a second royal capital. The Rococo palace was designed by court architects and served as the venue for the famous Grodno Sejm sessions of the 18th century. The last of these, in 1793, ratified the Second Partition of Poland under Russian military occupation — one of the final acts before the complete disappearance of the Polish-Lithuanian Commonwealth.
The castle was heavily damaged during the Second World War and reconstructed in a simplified form. Today it houses part of the local history museum, with exhibits on Belarusian applied arts, local crafts, and the history of the region. The interior is less impressive than the Old Castle, but the historical significance of the building is considerable.