as the Belvedere in their sales contract of November 1752. The complex was somewhat eclipsed by the other imperial palaces, and at first the buildings were left unused. Maria Theresa later created an ancestors' gallery of the Habsburg dynasty in the Lower Belvedere, as was the custom in all other palaces belonging to the imperial family. The palace was only once awakened from its slumbers in 1770 when a masked ball was staged there on 17 April to mark the occasion of the Imperial Princess Maria Antonia's marriage with the French Dauphin, who was later to become Louis XVI. The Lord High Chamberlain Prince Johann Joseph Khevenhüller-Metsch and the court architect Nicolaus Pacassi were charged with taking care of the extensive preparations for the ball to which 16,000 guests were invited. In 1776, Maria Theresa and her son, Emperor Joseph II decided to transfer the k.u.k. Gemäldegalerie ("Imperial Picture Gallery") from the Imperial Stables – a part of the city's Hofburg Imperial Palace – to the Upper Belvedere. Inspired by the idea of enlightened absolutism, the intention was to make the imperial collection accessible to the general public. The gallery opened five years later, making it one of the first public museums in the world. A series of eminent painters served as directors in charge of the imperial collection in the Upper Belvedere up to 1891 when it was transferred to the newly built Kunsthistorisches Museum (Museum of Fine Arts) on Vienna's splendid Ringstrasse. While the Upper Belvedere was transformed into a picture gallery at the end of the eighteenth century, the Lower Belvedere served chiefly to royal family members fleeing from the French Revolution. Most notably these included Princess Marie Thérèse Charlotte, the sole surviving child of Marie Antoinette and Louis XVI, and Archduke Ferdinand. Marie Thérèse Charlotte resided in the palace until her marriage with Prince Louis Antoine, Duke of Angoulême, in 1799. Archduke Ferdinand, the former Governor of the Duchy of Milan up to 1796, went to live there after the Treaty of Campo Formio in 1797. After the Habsburg Monarchy was forced to cede Tyrol to Bavaria in the Treaty of Pressburg in 1805, a new home had to be found for the imperial collection from Ambras Castle, near Innsbruck. At first, the collection was taken to Petrovaradin (now in Novi Sad, Vojvodina, Serbia) to protect it from looting by French troops. In 1811 Emperor Francis