The Karlskirche puts a Greek temple portico, a Roman oval dome in green copper, and two colossal free-standing columns into one front. The columns are copied from Trajan's in Rome and spiral with carved reliefs, and nothing structural requires them: they are there to claim that this emperor's authority came down from ancient Rome. A long shallow pool laid across the square reflects the whole facade, with a large modern sculpture set in the middle of the water as a deliberate counterweight.
Charles VI vowed the church while plague was killing Vienna in 1713, and Fischer von Erlach built it. The dedication flattered him twice, because the saint is Karl Borromäus and the emperor paying was Karl VI. Inside, everything pulls upward into the cupola, frescoed by Johann Michael Rottmayr with the patron saint rising through cloud. For twenty years a lift left over from restoration carried visitors up to see the brushwork at arm's length; it was dismantled in 2022, and the fresco is again something you look at from the floor.