The present building of the Diocesan Theological Seminary is located in a large courtyard at the former Jesuit College, between Brotstrasse and Neustrasse. It is a Holy Trinity Church or, simply Jesuit Church, as it is generally known in Trier.The church was initially constructed as the monastery church of the Franciscan order and was used by them from 1228 to 1570. In the following years, however, it was the collegiate church of the Jesuits until 1750. For several decades, it has been the church of the seminary. Among the oldest parts of the church are the choir and the adjoining apse, a single aisled structure, which was vaulted from the beginning.The choir windows are still the originals in the tracery set in in 1857. Each window arises from three very slender windows with pointed arches which grow into one window for the viewer through the shared sandstone frame and the low height of the middle window.At the beginning of the 18th century, the Jesuits expanded the choir by adding the side choirs, dedicated to St. Francis Xavier and St. Ignatius Loyala, the two founders of the Society of Jesus. The order was suppressed in 1773; the interior of the church has undergone a complete restoration.