The Porta Nigra (Latin for black gate) is a large Roman city gate in Trier, Germany. It is today the largest Roman city gate north of the Alps and has been designated a World Heritage Site.
The name Porta Nigra originated in the Middle Ages due to the darkened color of its stone; the original Roman name has not been preserved. Locals commonly refer to the Porta Nigra simply as Porta.
The Porta Nigra was built in grey sandstone between 186 and 200 AD. The original gate consisted of two four-storied towers, projecting as near semicircles on the outer side. A narrow courtyard separated the two gate openings on either side. For unknown reasons, however, the construction of the gate remained unfinished. For example, the stones at the northern (outer) side of the gate were never abraded, and the protruding stones would have made it impossible to install movable gates. Nonetheless, the gate was used for several centuries until the end of the Roman era in Trier.
In Roman times, the Porta Nigra was part of a system of four city gates, one of which stood at each side of the roughly rectangular Roman city. The Porta Nigra guarded the northern entry to the Roman city, while the Porta Alba (White Gate) was built in the east, the Porta Media (Middle Gate) in the south, and the Porta Inclyta (Famous Gate) in the west, next to the Roman bridge across the Moselle River. The gates stood at the ends of the two main streets of the Roman Trier, one of which led north-south and the other east-west. Of these gates, only the Porta Nigra still exists today.
In the early Middle Ages the Roman city gates were no longer used for their original function and their stones were taken and reused for other buildings. Also iron and lead braces were broken out of the walls of the Porta Nigra for reuse. Traces of this destruction are still clearly visible on the north side of the gate.
After 1028, the Greek monk Simeon lived as a hermit in the ruins of the Porta Nigra. After his death (1035) and sanctification, the Simeonstift monastery was built next to the Porta Nigra to honor him. Saving it from further destruction, the Porta Nigra was transformed into a church: The inner court of the gate was roofed and intermediate ceilings were inserted. The two middle storeys of the former gate were converted into church naves: the upper storey being for the monks and the lower storey for the general public. The ground floor with the large gates was sealed, and a large outside staircase was constructed alongside the south side (the town side) of the gate, up to the lower storey of the church. A small staircase led further up to the upper storey. The church rooms were accessible through former windows of the western tower of the Porta Nigra that were enlarged to become entrance doors (still visible today). The top floor of the western tower was used as church tower, the eastern tower was leveled, and an apse added at its east side. An additional gate - the much smaller Simeon Gate - was built adjacent to the East side of the Porta Nigra and served as a city gate in medieval times.
In 1802 Napoleon Bonaparte dissolved the church in the Porta Nigra and the monastery beside it, along with the vast majority of Trier's numerous churches and monasteries. On his visit to Trier in 1804, Napoleon ordered that the Porta Nigra be converted back to its Roman form. Only the apse was kept, and the eastern tower not rebuilt to its original height. Local legend has it that Napoleon originally even wanted to completely tear down the church. Allegedly, locals convinced him that the church had actually been a Gallic festival hall before being turned into a church. Another version of the story is simply that they told him about its Roman origins. It is claimed that this prevented the destruction of the building and persuaded Napoleon instead to convert the gate back to its original form.
In 1986 the Porta Nigra was designated a World Heritage Site, along with other Roman monuments in Trier and its surroundings.