Karlskirche (St. Charles's Church) at dusk - Karlsplatz in Vienna, Austria. The most outstanding baroque church in Vienna, as well as one of the city's greatest buildings, Karlskirche is dedicated to Saint Charles Borromeo. In 1713, one year after the last great plague epidemic, Charles VI, Holy Roman Emperor, pledged to build a church for his patron saint, Charles Borromeo, who was revered as a healer for plague sufferers.