During the Roman Empire, Trier was the largest city North of the Alps. It was surrounded by a strong fortress wall with four gates. The largest of them was the Northern gate, which is now called the Porta Nigra (Black Gate), and the Romans called them the Gate of Mars.
The Northern gate of the city was built in 170 AD. They were named after the God of war Mars, as the Field of Mars was located nearby, where men were trained for military service. The Porta Nigra were built of light blocks of sandstone, which weighed up to 6 tons. The stones were cut with perfect precision, connected to each other with iron brackets, and attached to the wall with liquid tin. For a long time, the gate had a light color, characteristic of sandstone, but then due to erosion, they became Black.
All the Roman buildings and fortress walls of Trier in the following centuries were dismantled for building materials, but the Porta Nigra is perfectly preserved due to the fact that in 1028 they were settled by the hermit Simeon of Trier, a monk of the Egyptian monastery of Saint Catherine. After his death in 1035, he was canonized, and the Church of Simeon of Trier was built based on the construction of the Porta Nigra.
During the Napoleonic wars, the German principalities came under the protectorate of France and Napoleon personally ordered the destruction of all Church buildings to free the masterpiece of Roman architecture from the later chaotic additions. The 12th-century Church building to the right of the gate has been preserved and now houses a Trier City Museum.
It is in the same way that the Roman temple of the Pantheon has reached our days in complete safety. It was built in 126 AD by the Emperor Hadrian. In 608, the Byzantine Emperor Phocas gave the Pantheon to Pope Boniface IV, who built a Christian temple here. This saved it from destruction.
