In 1973, during excavation works for the U-Bahn station, a mediæval chapel was discovered 12 metres under current ground level [4]. It was built around 1250 as a capella subterranea in the Magdalenenkapelle (the outline of which is shown on the pavement of the Stephansplatz). It is possible that it was originally intended as a chapel for burials, but at least by the 14th century had become a crypt for a mercantile family.