His major works include Schönbrunn Palace, Karlskirche, and the Austrian National Library in Vienna, and Schloss Klessheim, Holy Trinity Church, and the Kollegienkirche in Salzburg.

[4] During the seventeenth century, the Princes of Eggenberg had emerged as important patrons of the arts in Styria; through their patronage of Johann Baptist, they arranged for his talented son to travel to Italy and work in the flourishing artistic environment of the late Italian Baroque.

Commissions were plentiful, as royalty and highest echelons of aristocracy sought to repair the damage inflicted on their country residences by the Ottoman Turks in the course of their 1683 campaign.

Fischer's understanding of an urbane Baroque idiom appeared superior to that prevalent in Central Europe, and in 1687 he secured the key position of court architect, which he would retain in the service of three emperors.

As Hans Aurenhammer put it, this edifice represented "a new type of town palace characterized by impressive form, structural clarity, and the dynamic tension of its decoration".

In this structure, completed by his son Joseph Emanuel, Fischer's ambition was to harmonize the principal elements and ideas that underlie the most significant churches in the history of Western architecture: the Temple of Solomon in Jerusalem, Hagia Sophia in Constantinople, the Pantheon and Saint Peter's Basilica in Rome, the Dome des Invalides in Paris and Saint Paul's Cathedral in London.