Colonia Claudia Ara Agrippinensium was the Roman colony in the Rhineland from which the city of Cologne, now in Germany, developed.

It was usually called Colonia (colony) and was the capital of the Roman province of Germania Inferior and the headquarters of the military in the region.

In 38 BC, the Germanic tribe known as the Ubii, who inhabited the right bank of the Rhine, were resettled by the Roman General Marcus Vipsanius Agrippa in the lands in the Cologne Lowland vacated by the Eburones.

During the rule of Augustus (30 BC to AD 14), the Ara Ubiorum (Altar of the Ubii) was constructed within the city limits.

[1][2] This altar was possibly foreseen as the central place of worship for a greater Germanic province, which would comprise lands across the Rhine, which remained unconquered at this point.

After Arminius' victory over Publius Quinctilius Varus in the same year at the Battle of the Teutoburg Forest, the plans for a greater German province were largely set aside.

After the Battle of the Teutoburg Forest, Germanicus made efforts to stabilize the border region and to plan and carry out new offensives against the Germanic tribes located on the right bank of the Rhine.

With the death of Augustus in AD 14 the legions garrisoned in Cologne mutinied with the aim of establishing Germanicus as emperor.

She succeeded in convincing Claudius around 50 AD to elevate her birthplace to a colonia named Colonia Claudia Ara Agrippinensium (Colony of Claudius and Altar of the Agrippinians) − where the name of the emperor stands for the rights granted to a colonia, that of the empress for the inhabitants, her compatriots, who she had named Agrippinenses after her, and even the altar at the central sanctuary (on the forum) was mentioned, the Ara Ubiorum, where, in addition to the emperor, the Ubiian gods were worshiped.

The Roman Senate installed Servius Sulpicius Galba as emperor, but he was quickly murdered by another contender for the throne, Marcus Salvius Otho, who had the backing of the Praetorian Guard.

However, when the Batavians demanded that the city wall be torn down, the inhabitants of Colonia again sided with the Roman Empire.

Vitellius was overthrown eight months later by Titus Flavius Vespasianus, whose troops feared reprisals for having previously recognized Otho as emperor.

Ten years later, the colonia became the capital of the Roman province of Lower Germany, Germania Inferior, with a total population of 20,000 people[3] with around 15,000 of them inside and around 5,000 outside the city walls.

The Alteburg naval fort was a camp measuring around twelve hectares, surrounded by a vicus, a civilian settlement, just three and a half kilometers south of the ancient city, in the eastern area of today's Marienburg district of Cologne.

The legions of the province were stationed in Vetera II near Colonia Ulpia Traiana (near present-day Xanten), Novaesium and Bonna.

It is the only administrative building of this type in the entire Roman Empire in which the name praetorium as such is preserved in an inscription.

The archaeological strata of that time indicate that conquest and looting had catastrophic effects and the city lay in ruins.

The last dated reconstruction is from 392/393, when Arbogast, the Magister Militum of the Western half of the Empire, in the name of the emperor Eugenius renewed an unspecified public building.

When Franconian kingdoms (such as Austrasia) formed with the fall of Roman rule, the Roman-influenced urban settlements in the Rhineland also largely disappeared.

But precisely because Cologne grew rapidly in the Middle Ages and beyond, many Roman buildings disappeared in the course of new development.

In return, Cologne received twelve Romanesque churches, in addition to an immense cathedral, and again acquired great prosperity through trade and customs on the Rhine as well as through exquisite craftsmanship[9] that far exceeded that which was already advanced in antiquity.

It was designed according to a uniform concept, was based on the topographical conditions of the site and essentially reproduced the contours of the flood-free plateau.

As in every major Roman city, the forum district was located in the center of the CCAA, at the intersection of Cardo and Decumanus Maximus.

The existence of an early Christian cult space in Cologne is reported by Ammianus Marcellinus in the year 355.

It could also be that this spot, directly on the northern wall of the ancient city, was originally the private house in which the first (perhaps still illegal) early Christian community met to hold services and baptisms.

In Summer 2018, archaeologists declared that the foundations (located at 50°56′09.6″N 6°57′12.8″E / 50.936000°N 6.953556°E / 50.936000; 6.953556) that they discovered in 2017 during excavations to build a Protestant church, might be related to the "oldest known library in Germany", dating back to the 2nd century.

[16] There is also an array of Roman and medieval jewellery, artefacts of everyday life, ivory and bone objects, bronzes, coins, wall paintings, grave stones, inscriptions, pottery and architectural fragments.