According to certain sources, the cathedral was commissioned by Emperor
Constantine the Great and built on top of a palace of
Saint Helen, his mother. Following the conversion of Constantine to Christianity,
bishop Maximin (329-346) is said to have coordinated the construction of a cathedral, which at the time was the grandest ensemble of ecclesiastical structures in the West outside
Rome. On a groundplan four times the size of the present cathedral no less than four
basilicas, a
baptistry and outbuildings were constructed. Archaeological research confirms that the current cathedral, as well as the adjacent cloisters and
Church of Our ...., is raised upon the foundations of ancient Roman buildings of
Augusta Treverorum. The four piers of the crossing of the present church, as well as parts of the brick outer walls are remnants from this period.