The festive opera "Constanza e Fortezza" (Constancy and Strength), with a libretto by Pietro Pariati (1665–1733), was Fux's most notable opera. It was performed twice in a specially designed open-air theatre in Prague Castle in the occasion of the coronation of Charles VI as King of Bohemia in 1723. The set was designed by the court theatre architect Giuseppe Galli-Bibiena (1696–1756). This work is regarded as a festive coronation opera because both performances of this opera took place a few days before the coronation of Charles VI as King of Bohemia and of his consort Elisabeth Christina as Queen. There was an issue of the double celebratory function of this opera – coronation of Charles VI and Elisabeth Christina's birthday.