The gate dates back to a time (about A.D. 180) when the Romans often erected public buildings of huge stone blocks (here, the biggest weigh up to six metric tons).

 
The slabs were cut by bronze saws powered by mill wheels (some cutting traces are still visible) and put together without mortar. Instead, two stones each were held together horizontally by iron clamps whose bent ends were embedded in corresponding holes by molten lead. One clamp is visible inside the gate near the eastern spiral staircase; rust traces can be seen in many holes on the outside because in the Middle Ages people chiseled these holes to retrieve the metal for recycling.

The stone blocks were spared from recycling because of the Greek monk Simeon, who had himself walled up in the eastern tower as a hermit in 1028. After his death in 1034/5, he was buried inside the gate and made a saint. In his honor, two churches were built into the gate (torn down 1804-1819). The upper story of the eastern tower was razed - the only real damage to the stone gate, whose name, "Black Gate," is medieval and goes back to the black pollution patina on the gray sandstone. Inside, traces of the double church, Roman stone masons' marks, and date inscriptions are visible.

Opening hours:
January 1 - March 31: 9 a.m. - 5 p.m.
April 1 - September 30: daily 9 a.m. - 6 p.m.
October 1 - November 30: 9 a.m. - 5 p.m.
December 1 - December 31: 9 a.m. - 4 p.m.

Note:
Last admission 30 minutes before closing.

For security reasons, the Porta Nigra may be closed in dangerous weather (ice and snow).

Cost: € 2.10/€ 1.00