The oldest part of the Hofburg is the Alte Burg (Old Fortress), which has remained from the primary medieval fortress complex.
Since the 18th century, this part has been called the Schweizertrakt (Swiss Wing) which is a reference to the Swiss mercenaries who served as the palace watch or as bodyguards for Emperor Franz Stephan. This wing houses the Imperial Treasury (Schatzkammer), in which, the Imperial Insignia of the Holy Roman Empire (Reichskleinodien) and the Empire of Austria are kept. The Swiss Wing also includes a Gothic chapel (Burgkapelle) from the fifteenth century, in which the Vienna Boys' Choir still sings on Sundays in it. The Swiss Court yard (Schweizerhof) was built during the reign of Emperor Ferdinand I in the style of the Renaissance. Its famous red-black Gate (Schweizertor) was built in 1552 and displays the many titles of Emperor Ferdinand I and the insignia of the Order of the Golden Fleece (Vliesordens). It also includes a well (Schweizerhofbrunnen),
located in one side of the gate.
Inscription above the gate reads:
BOEM[IAE] ZC REX INFA[NS]
HISPAN[IAE] ARCHI[DUX] AVSTR[IAE]
DVX BVRGVND[IAE] ZC
Freely translated as:
"Ferdinand, Holy Roman Emperor, King in Germany, Hungary, Bohemia etc,
Prince-Infante in Spain, Archduke of Austria, Duke of Burgundy etc, in the year 1552"