[3] In the course of Augustus' expansionist endeavours starting in 16 BCE, his stepson Nero Claudius Drusus also advanced to the Middle Rhine and secured the area for the Roman Empire.

The aqueduct carried fresh water over a distance of nine kilometres from the springs in today's distant Mainz districts of Finthen [de] (Fontanetum) and Drais to the legionary camp on the Kästrich.

[10] Rather, the presence of Roman troops, who repeatedly had to deploy large detachments for campaigns in distant areas and were distracted by a series of civil wars, was probably no longer considered sufficient to protect the city against raiders.

With the abandonment of the Upper Germanic Limes, Mogontiacum once again became a border town - despite further use of areas on the right bank of the Rhine, such as the Castellum bridgehead or the thermal baths in neighbouring Aquae Mattiacorum [de] (Wiesbaden).

Despite the development of urban structures, including large buildings and its function as provincial capital from the year 90, Mogontiacum did not have an official city title such as colonia, municipium or civitas.

[30] The first mention of Mogontiacum as a civitas dates back to the years of the first tetrarchy (after 293 to 305),[31] at a time when these differentiations in city titles had already been more or less abolished by Caracalla's general grant of citizenship (Constitutio Antoniniana in 212).

[34] After Tiberius renounced the permanent occupation of Magna Germania with the desired Elbe border, the organisation of the areas on the left bank of the Rhine remained in a provisional administrative stage.

[36] The previous military commander of the Upper Germanic army group (legatus Augusti pro praetore), who was also responsible for civil administration, became the consular governor of the newly founded province, to whom the troops stationed there continued to report as usual.

The earliest archaeological evidence of a civilian settlement dating back to Augustan times can be found directly in front of the Porta praetoria (today's Emmerich-Josef-Straße [de]).

During construction work in the 1970s, extensive architectural remains, a marble fountain with a bronze fish figure as a waterspout and bricks with the stamps of the Mainz legions were found.

Only the size of the stage theatre, which could accommodate around 10,000 spectators, and the general development of the city allow certain conclusions to be drawn about a possible civilian population, which may have been in the lower five-digit range.

[67] The monument also became the focus of annual cult and commemoration ceremonies (supplicatio) in honour of Drusus, which were attended by delegates from the provincial councils of the three Gallic provinces (concilium Galliarum).

A large part of the arch (43 of a total of 75 individual sandstone blocks) was discovered as spolia between 1898 and 1911 during the demolition of the medieval city wall in the lower, late Roman foundation area.

Numerous dedication stones, exclusively from legionary legates, point to a sanctuary of Apollo and another unknown deity in the 3rd century in the immediate vicinity of the Rhine bridge.

The date of construction, size and furnishings indicate that the sanctuary was held in high esteem and played a major role in the spread of the cult in the two Germanic provinces.

[85] The joint cult complex of Isis and Mater Magna, however, which was discovered in 1999, was excavated under archaeological supervision, conserved and presented to visitors as a museum together with some of the rich finds from religious and cultic life.

In 2020, archaeologists excavating in the area of the customs harbour found a life-size, elaborately crafted but headless statue of a female figure with her foot resting on a calf's head.

In addition to its hoped-for healing effect for the emperor and the state, the foundation and the erection of the statue in a public space also increased the prestige of the donors and their civilian settlement.

[43] In view of the number of soldiers stationed there, at times up to four legions including auxiliary troops, it can be assumed that Mogontiacum quickly became an important centre for local and long-distance trade.

[93] In the individual vici of Mogontiacum, entire craftsmen's quarters developed, such as a significant collection of shoemakers' workshops along the camp road down to the Rhine in the area of today's Emmeransstraße.

[42] A larger thermal bath building was built in the year 33 in the immediate vicinity of today's State Theatre and thus at the fork in the main road coming from the legionary camp.

A graffito on a shard of clay from the 2nd century gives the governor's address as "... praetorium ... ad hiberna leg XXII P P F" and is regarded as evidence in favour of this hypothesis.

They were increasingly responsible for supplying Mogontiacum with food and other agricultural goods, with the result that the civilian settlement gradually assumed the central market function for the surrounding area.

[108] In the Gonsbach valley, which is part of the Gonsenheim district of Mainz, surprisingly large ruin complexes and the high-quality relief of a bound Teuton were found at the end of 2013 during "renaturalisation" measures.

A larger circular structure with a diameter of 40 m resembles an oval track or a lungeing course in modern equestrian sport, so that this was possibly a facility for Roman cavalrymen and their training - also in view of the favourable location of the stream and meadows for keeping animals.

The site has since been identified by the responsible archaeologists from the Mainz Archaeology Directorate, Marion Witteyer, as a stud farm from late antiquity, which was possibly operated by the military stationed in Mogontiacum.

He was directly followed by Johannes Huttich, who published his work Collectana antiquitatum in urbe atque agro Moguntino repertarum in 1520 with the support of Elector Albert of Brandenburg.

After drastically decimating the stock of Roman stone monuments in this way (some of these pieces can still be found today in the Reiss-Engelhorn-Museums of the city of Mannheim), he commissioned the Benedictine priest Joseph Fuchs to write a comprehensive work on the history of Mainz in return.

Its collection of Roman stone monuments quickly grew in importance and also attracted famous guests such as Johann Wolfgang von Goethe, who wrote about it several times.

[130] In the basement of the Römerpassage in Mainz city centre [de], numerous small finds that came to light during the excavations are exhibited together with the structural remains of the Isis and Mater Magna sanctuary found there.