From the time of Diocletian's reorganization of the divisions of the empire, Augusta Treverorum, now Trier, was the capital of Belgica Prima, the chief city of Gaul, and frequently the residence of the emperors.

[1] An 11th-century tradition states that he had been a priest of Antioch, and that he was moved to the See of Trier by Pope Sylvester I at the request of the Empress Helena.

"[1] Medieval tradition dates to Agricius' time the construction of the first cathedral in Trier, which was said to have been built over the Empress Helena's palace which she gave for that purpose.

[2] The Heiliger Rock (the "Holy Gown") is said to be the robe (the "seamless garment") which Jesus wore before His crucifixion and for which, according to the Gospel of St. John, the Roman soldiers cast lots.

The famous relics of Trier - the above-named "Heiliger Rock", the Nail of the True Cross, and the body of Matthias the Apostle - are all said to have been brought there by Agricius.