Trier, formerly known in English as Treves, is a city in Germany on the banks of the Moselle. Trier lies in a valley between low vine-covered hills of red sandstone in the west of the state of Rhineland-Palatinate, near the border with Luxembourg and within the important Moselle wine region. Founded by the Romans in the late 1st century BC as Augusta Treverorum (Latin for "The City of Augustus among the Treveri"), Trier may be the oldest city in Germany. It is also the oldest seat of a bishop north of the Alps. In the Middle Ages, the Archbishop of Trier was an important prince of the church, as the Archbishopric of Trier controlled land from the French border to the Rhine. The Archbishop also had great significance as one of the seven electors of the Holy Roman Empire.
With an approximate population of 105,000, Trier is the 4th-largest city in its state, trailing Mainz, Ludwigshafen, and Koblenz. The nearest major cities are Luxembourg ( to the southwest), Saarbrücken ( southeast), and Koblenz ( northeast).
Trier is home to the University of Trier, the administration of the Trier-Saarburg district and the seat of the ADD (Aufsichts- und Dienstleistungsdirektion), which until 1999 was the borough authority of Trier, and the Academy of European Law (ERA). It is one of the five "central places" of the state of Rhineland-Palatinate. Along with Luxembourg, Metz and Saarbrücken, fellow constituent members of the QuattroPole union of cities, it also forms a central place of the greater region encompassing Saar-Lor-Lux (Saarland, Lorraine and Luxembourg), Rhineland-Palatinate, and Wallonia.
The historical record describes the Roman Empire subduing the Treveri in the and establishing Augusta Treverorum in 16 . The name distinguished it from the empire's many other cities honoring the first emperor Augustus. The city later became the capital of the province of Belgic Gaul; after the Diocletian Reforms, it became the capital of the prefecture of the Gauls, overseeing much of the Western Roman Empire. In the 4th century, Trier was one of the five biggest cities in the known world with a population around 75,000 and perhaps as much as 100,000. The Porta Nigra ("Black Gate") dates to this era. A residence of the Western Roman Emperor, Roman Trier was the birthplace of Saint Ambrose. Sometime between 395 and 418, the Roman administration moved the staff of Praetorian Prefecture from the city to Arles. The city continued to be inhabited but was not as prosperous as before. However, the city remained the seat of a governor and had state factories for the production of ballistae and armor and woolen uniforms for the troops, clothing for the civil service, and high-quality garments for the Court. Northern Gaul was held by the Romans along a line from north of Cologne to the coast at Boulogne through what is today southern Belgium until 460. South of this line, Roman control was firm, as evidenced by the continuing operation of the imperial arms factory at Amiens.
As part of the Prussian Rhineland, Trier developed economically during the 19th century. The city rose in revolt during the revolutions of 1848 in the German states, although the rebels were forced to concede. It became part of the German Empire in 1871.
In June 1940 over 60,000 British prisoners of war, captured at Dunkirk and Northern France, were marched to Trier, which became a staging post for British soldiers headed for German prisoner-of-war camps. Trier was heavily bombed and bombarded in 1944 during World War II. The city became part of the new state of Rhineland-Palatinate after the war. The university, dissolved in 1797, was restarted in the 1970s, while the Cathedral of Trier was reopened in 1974. Trier officially celebrated its 2,000th anniversary in 1984.