The Constantine-Basilica stands for the political aspect of the diffusion of Christianity in our region. Cathedral-Information and Museum of the Episcopal Diocese stand for the first evidences of the oldest early Christian communities north of the Alps.

Trier (Augusta Teverorum) evidentially had a Christian community in the 3rd century. Helena, mother of Emperor Constantine, counts as originator of Christianity north of the Alps. At the instigation of bishop Agritius (260-329/333/335) her residential buildings were adapted to two basilicas - the first twin plant cathedral (today Cathedral-Information) at the emperor’s palace. This conversion of the palace under Agritius is confirmed by archaeological excavations underneath the Cathedral-Information. After the attacks of the Germans and the capture of Trier by the Franconians in 470 both basilicas were destroyed. Later a bit north of the former cathedral a new one was built. The construction of the present cathedral on the fundament of the second cathedral happened in the time between 1016 – 1047. The cathedral of Trier counts as Germany’s oldest church. 

The Museum of the Episcopal Diocese makes the early Christian image of Jesus accessible to the visitor. The origin of the museum dates back to the ancient Lipidarium of cathedral and Church of Our Lady, where from the 18^th century on remains of altars, tombs and other relics were collected. Later the building was used as the prison of Trier until the museum was installed there in 1988. The confrontation of antique and contemporary creations initiates a dialogue aiming to involve and to inspire the beholder.

Between 306 and 350 Trier was the residency of the Roman Emperor Constantine The Big and his sons and later from Valentinian and Gratian (364 – 383). The Palace Foyer - Constantine Basilica – since then was the emperor’s residency and centre of Roman politics. At the beginning of the 4th century it served representative purposes. Probably the foyer was built latest under Constantine The Big who reigned from 306 to 337. In 313 Emperor Constantine confirmed Christianity as equal state religion.

The building received the name basilica from the local historian Johannes Steiner in the 19^th century. The expression basilica is related to the passed on eulogy of Eumenius von Autun that was read out in the presence of Emperor Constantine and describes the palace-foyer as basilica. Therefore palace-foyer (aula palatine, palatium) is the correct name for Roman profane buildings. The palace foyer in Trier was the best amongst others like Arles and Milan. When Constantine in 330 finally shifted his residency to Constantinople it lost more and more importance.

After the migration in the 5^th century Trier fell under Franconian power; roof and gallery of the palace-foyer collapsed, the palatium dilapidated and the roman walls around from now on enclosed the courtyard for stables and housings. In the Middle Ages the walls served as protection against attacking enemies. In the 17^th century during the construction of the Electorial Palais under Philip Christof von Sötern (1623 – 1651) a nine metres tight three-storey accommodation wing which integrated apsis and west wall replaced the 27 metres wide palace-foyer. In the course of secularization the French used the palace as barracks and military hospital until the Prussian Military took it over in 1814.

In default of room for the Evangelic Church Community in Trier Friedrich Wilhelm IV, King of Prussia, decided to change back the Constantinian palace-foyer in its original state and to leave it to the evangelic community of Trier as basilica. The inauguration occurred on September 28 in 1856.

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