The Evangelical Church of the Redeemer (Basilica of Constantine) was originally an audience hall for the Roman emperors who resided in the city in the 4th century. In 1614, the south and east walls were demolished and the rest was incorporated into the bishop's new residence, the Electoral Palace. Between 1844 and 1856, the building was restored and donated to the Protestant cult. Severely damaged by an American air raid, it was rebuilt in the 1950s. Since 1986, the Basilica of Constantine has been a UNESCO World Heritage Site.
The Church of Our Lady was founded around 1230 and is, together with the Elisabeth Church in Marburg, the oldest Gothic church in Germany. The church owes its origin to the former cathedral complex of the 4th century, which consisted of a double church. Built as a separate church but liturgically close to the cathedral, the two were finally separated in 1803. In the second half of the 19th century, a major restoration took place. As a result, part of the baroque furniture was replaced by neo-gothic furniture.
Trier Cathedral is Germany's oldest cathedral, built between 310 and 320 in the time of Constantine the Great (306-337). The first cathedral in the 4th century was destroyed by the Franks, and a further destruction took place in 882 during Viking raids in the Rhineland. The most important building phases that followed were in the 10th century (under Bishop Egbert), in the 13th century (for the interior of the cathedral), from the 14th to the 16th century (for the exterior). Restorations were undertaken in the 19th century, to restore it to its medieval appearance, and after the Second World War. Since 1986, Trier Cathedral has been listed as a UNESCO World Heritage Site.