The Coelestine Church, between the Stadtplatz and the Enns, was founded in the 17th century as the chapel of a convent of Celestine nuns. The convent buildings later housed a tax office and a school; the church survives as a small Baroque set piece with a single nave and a fine altar painting.
It is most often visited in passing, as it sits between the Stadtplatz and the Michaelerbrücke. Worth ducking in if open.