This enormous rectangular building jointed around four interior courtyards interconnected by a magnificent vestibule was commissioned for Luigi Vanvitelli by Charles III of Bourbon. The main stairway leads to sumptuous royal apartments furnished in neoclassical style. You can see the 18C apartment, with its walls covered in frescoes (J.P. Hackert) representing the four seasons and the Queen's apartment, which is quite charming, decorated in a rocaille style.