1969 a private company (Hofburg Vienna – Wiener Kongresszentrum Hofburg Betriebsgesellschaft) has been managing the international congress and events centre. Every year the convention centre hosts about 300 to 350 events, with around 300,000 to 320,000 guests. Among the events are conventions and meetings as well as banquets, trade fairs, concerts, and balls. Swiss Wing The oldest parts of the palace date from the 13th century and were primarily constructed by the last of the Babenbergers, or by Ottakar II of Bohemia. Before that the castle of the Austrian rulers had been located on the square called "Am Hof", which is near the Schottenstift (Scottish Monastery). The castle originally had a square outline, with four turrets, and was surrounded by a moat with a drawbridge at the entrance. These oldest sections of the castle today form the Swiss Court (Schweizerhof), where there are a gothic chapel (Burgkapelle), dating from the 15th century, and the treasury (or Schatzkammer), affiliated to the Kunsthistorisches Museum which holds, among other things, the imperial insignia of the Holy Roman Empire (Reichskleinodien) and of the Empire of Austria. The Court Music Chapel (Hofmusikkapelle) is located inside the Court Chapel () and is where the Vienna Boys' Choir traditionally sing mass on Sundays. The appearance of the Swiss Court dates from the Renaissance, during the reign of the Emperor Ferdinand I. The Swiss Gate entrance (Schweizertor) displays the many titles of Ferdinand I and the insignia of the Order of the Golden Fleece are painted on the ceiling. An adjoining section of the Swiss Wing houses the Radetzky Apartments. In recognition of his services in the Italian campaign during the revolutionary year of 1848, the Emperor Franz Joseph I permitted the worthy Field Marshal Radetzky to live in these apartments, even though he was not a member of the imperial family. In the Knight's Hall (Rittersaal), on 15 May 1717 the Empress Maria Theresa was baptised by the Papal Nuncio Giorgio Spinola, representing Pope Clement XI, with baptismal water containing a few drops from the River Jordan. Next to the Knight's Hall is the Guard Room (Trabantenstube), where the duty officer of the Household Guards kept watch over the emperor. The lower section of this wing once accommodated the imperial kitchen. Amalienburg Across from the Swiss Gate is the Amalienburg, named after Empress Amalie Wilhelmine, the widow of Joseph I. However, this wing had already been in