The Porta Nigra, which means "Black Gate", considered to be the hallmark of Trier and listed as a World Heritage site by UNESCO. Built in 180, in the heyday of the Roman Empire, they are the oldest preserved defensive works in Germany. Trier at the time, still called "Northern Rome", was surrounded by high walls with four entrance gates. The only preserved and today affects its strength and greatness. Their width is 36 meters, height 30 meters and depth of 21, 5 meters.

Contrary to its name Porta Nigra built of white stone, darkened by time. 7200 boulders unique structures, each weighing up to 6 tons, connected without cement: carefully tailored they were connected with iron clamps and secured with liquid tin. In the Middle Ages for the precious metal bracket partially got through the holes. However, despite the numerous wars and robberies, the construction of a fully survived.

Legend links the preservation of this black gate with a hermit monk Simeon, who lived in them for 1028 years, 1035 and was buried according to his will, under the gate. After his death, to the Porta Nigra it was attached to the church, called the Church of Saint Simeon. By order of Napoleon in 1803, the church was almost completely destroyed, and the gates have gained its original appearance. Today, the Porta Nigra is a museum.