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, like the other roman monuments of the town, it has been designated a UNESCO World Heritage Site in 1986.
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.
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.
The modern appearance of the Porta Nigra goes back almost unchanged to the reconstruction ordered by Napoleon. At the south side of the Porta Nigra, remains of Roman columns line the last 100m of the street leading to the gate. Positioned where they had stood in Roman times, they give a slight impression of the aspect of the original Roman street that was lined with colonnades.
The gate is today closed for cars, but stands right next to one of the main streets of Trier. In addition to the general pollution, the exhaust fumes of the passing cars have been damaging the stones for decades. Generally, however, the Porta Nigra is still in remarkable condition.
The Porta Nigra, including the upper floors, is open to visitors. In summer, guided tours are also offered by an actor dressed up as and portraying a centurion (a Roman army officer) in full armour.