Those sections of the city situated to the south and east of the lower town are designated the upper town (haut de la ville). The area straddles a ridge of higher ground denoted by a series of hills— Coudenberg, Treurenberg, and Galgenberg—and embraces locales around the Grand Sablon and Petit Sablon squares, Mont des Arts, Parc de Bruxelles, and beyond to the avenue Louise and Léopold district.
Development of the upper town dates from the ducal fortress begun by Lambert II. The royal presence was followed by administrative offices and stately town houses. Public buildings and monuments followed. As such, the upper town has always been associated with royalty and government, the aristocracy and the upper bourgeoisie. Distinguishing features include monumental squares joined by classical boulevards. The official residence of the royal family, the Belgian federal parliament, federal government ministries, the Palais de Justice, and major museums are located here.
Historical Dictionary of Brussels. Paul F. State.