Regalia to the Karlštejn Castle near Prague, which he had just built for that purpose. in 1424, with Bohemia suffering the troubles of the Hussite Wars, Sigismund had them relocated to Visegrád and then to Nuremberg, where they were permanently kept in the Heilig-Geist-Spital except for the time of coronations (in Aachen until 1531, then in Frankfurt from 1562). In 1796, as the war with revolutionary France was threatening the entire fabric of the Empire, the Regalia were brought for safety to Saint Emmeram's Abbey in Regensburg, and from there in 1800 to the Imperial capital in Vienna, where the Empire was abolished on 6 August 1806. The crown and other Regalia remained in Vienna until the Anschluss of March 1938, when they were brought back to Nuremberg (this time in the Katharinenkirche) by Nazi Germany in line with their promotion of the city as repository of mythicized ancient German traditions. During World War II the crown was placed in the Historischer Kunstbunker, an underground vault of Nuremberg Castle. The American military recovered it with other treasures in August 1945, and returned it to the Oesterreichische Nationalbank in allied-occupied Austria in January 1946. It has been kept permanently in Vienna since that date. The Crown and Regalia were again on display at the Hofburg in 1954. The current display dates from a comprehensive refurbishment of the Hofburg's Treasury Vault in 1983-1987. Design The crown does not have a round shape but an octagonal one, a possible reference to the shape of crowns of Byzantine emperors and/or of Charlemagne's Palatine Chapel in Aachen. Its eight hinged plates are arched at the top. Two strips of iron of unidentified date, riveted with golden rivets to the plates, hold the crown together. Before the addition of the rings the plates were held together by long golden pins, which made it possible to separate the plates and the arch for easier transport. Each plate of the crown is made out of a high carat gold, around 22 carats, which gives the crown a "buttery" colour, and is studded with pearls and precious stones. The stones are not cut into facets (a technique still unknown when the crown was made), but polished into rounded shapes and fixed en cabochon, i.e. put into openings that were cut into the metal, and fastened with thin wires. The effect is that when light shines in, the stones look