sentences:  In 1973, during excavation works for the U-Bahn station, a mediaeval chapel was discovered 12 metres under current ground level .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.