the High Cathedral of Saint Peter in Trier, or Trier Cathedral, is a Roman Catholic cathedral in Trier, Rhineland-Palatinate, Germany. It is the oldest cathedral in Germany and the largest religious structure in Trier, notable for its long life span and grand design.
The central part of the nave was built of Roman brick in the early fourth century, resulting in a cathedral that was added onto gradually in different eras.
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.