The Dom St. Peter in Trier is the oldest Christian church in Germany — a continuous place of worship since the 4th century, when the Roman imperial residence stood on this ground. The current structure integrates Roman foundations, a Romanesque nave, and Gothic chapels added over twelve centuries of building and rebuilding. It is a UNESCO World Heritage Site.
The interior is vast and layered — ancient Roman columns, Romanesque stonework, Baroque altars and frescoes all coexisting. The Treasury (Domschatzkammer) houses an exceptional collection of reliquaries, including the ivory-carved portable altar of St. Andrew (10th century) and a 3rd-century sarcophagus. Allow at least an hour.
Directly attached to the cathedral is the Liebfrauenkirche, a separate 13th-century Gothic church built on a radiating plan — considered one of the earliest examples of French High Gothic architecture in Germany. Both are free to enter; the treasury charges admission.