Moguntiacum

or Mogontiacum (Mainz)

A city and fortress on the left bank of the river Rhenus (Rhine), opposite its junction with the Menus (Main). The name of the place, derived from a Celtic deity Mogon or Mogontia, presupposes a pre-Roman settlement.

Under Augustus (15–12 BC) a fortified legionary camp was built half a mile from the Rhine as a base for the invasion of `Free Germany,’ into which the site commanded important routes. In 9 BC Tiberius erected a funeral monument at Moguntiacum in honor of his late brother, Nero Drusus (Drusus junior). On January 1st, AD 69, the two legions of its garrison overthew the statues of Galba, thus launching the civil war, and were joined soon afterward by their fellow soldiers in Lower Germany, who set up their governor Vitellius as emperor. Later in the same year the Gallo-German rebellion of Civilis, after his first attack had been repelled by Dillius Vocula, destroyed the city, together with all other strongholds as far as the sea. Under Domitian (81–96), the timber fortress was replaced by stone, while a civilian settlement grew up beside it. In 83–85 Moguntiacum was Domitian's base for his operations against the German tribe of the Chatti, and, for the same purpose, a fort was constructed across the river (at Kastel), linked to the town by a bridge. After the rebellion of his governor Lucius Antonius Saturninus in 89, the garrison of two legions was reduced to one; but when the two German commands were converted into provinces a year or so later, Moguntiacum became the capital of Upper Germany, of which it stood at the northern extremity.

In 234 the emperor Severus Alexander, after German incursions had compelled him to concentrate a large western army on the Rhine, established his headquarters at the city, spanning the river with a pontoon bridge (later replaced by a permanent bridge—shown on a lead medallion—of which the piers were seen and described in modern times, though subsequently destroyed). However, Alexander's undignified attempts to pay off the Germans caused his soldiers to murder him and his mother, Julia Mamaea, at the camp (235). When Postumus (260–68) set up a secessionist empire of the western provinces, one of his senior officers, Laelianus, declared himself emperor at Moguntiacum. Postumus took the city by siege and put Laelianus to death, but his refusal to allow his own men to engage in looting caused him to be assassinated shortly afterward. In 286–88 Maximian, joint emperor with Diocletian, successfully averted a mass attack on Moguntiacum by Alamanni and Burgundians.

In about 355 (some say earlier) the place became a citizen community, with the rank of municipium, and at about the same time or perhaps not before the reign of Valentinian I (364–75), the town walls—originally dating from the third century—were reconstructed to follow a new course, embracing part of the area of the military fortress that had been abandoned. At this period the city was the capital of the province Germania Prima and the headquarters of the dux Moguntiacensis, the military commander of a sector of the Rhine frontier; it was also the seat of a bishopric. When, however, the Germans crossed the frozen river en masse at the end of 406, Moguntiacum was the first place to fall; it was looted and many of its inhabitants, who had taken refuge in a church, were massacred. The city remained in the hands of the Burgundians, who shortly afterward encouraged the surviving population to proclaim a Gallo-Roman named Jovinus as dissident Roman emperor (411–13).

The arches of a first-century aqueduct (the Römersteine) can be seen at Mainz-Zahlbach, and fragments from various other buildings have been found incorporated in subsequent constructions.