The largest growth of Nuremberg occurred in the 14th century. Charles IV's Golden Bull of 1356, naming Nuremberg as the city where newly elected kings of Germany must hold their first Imperial Diet, made Nuremberg one of the three most important cities of the Empire. Charles was the patron of the Frauenkirche, built between 1352 and 1362 (the architect was likely Peter Parler), where the Imperial court worshipped during its stays in Nuremberg. The royal and Imperial connection grew stronger in 1423 when the Holy Roman Emperor Sigismund of Luxembourg granted the Imperial regalia to be kept permanently in Nuremberg, where they remained until 1796, when the advance of French troops required their removal to Regensburg and thence to Vienna.