The Karlskirche (“St. Charles Church”) could be called Fantasia on Imperial Majesty. In A.D. 1713, riding high on the retreat of the Turkish threat and his new position as Holy Roman Emperor, Charles VI decided to build a church for his patron saint, the fanatically anti-Protestant St. Charles Borromeo. Plague had visited Vienna the year before, and Charles VI had vowed he would honor Borremeo, famed for helping plague victims in Italy, if the city made it out alive. Construction crews started work in A.D. 1716.
The final product, a Baroque wedding cake if ever you saw one, is the work of the great architect Johann Bernhard Fischer von Erlach. It was built in direct view of the Hofburg and was used as the imperial patron parish church until the Empire disintegrated.
Hollywood Bonus: The famed actress and inventor Hedy Lamarr (then known as Hedwig Kiesler) was married in Karlskirche in A.D. 1933. She was 19. Her fascist husband, Friedrich Mandl, was 32. The marriage was not a happy one. A few years later, Hedy disguised herself as a maid and fled to Paris. The rest is Tinseltown history.