 The Diocese of Strasbourg was first mentioned in 343, belonging to the ecclesiastical province of the Archbishopric of Mainz since Carolingian times.Archeological diggings below the current Saint Stephen’s Church, Strasbourg (Saint-Étienne) in 1948 and 1956 have unearthed the apse of a church dating back to the late 4th or early 5th century, considered the oldest church in Alsace.It is supposed that this was the first seat of the diocese.