Located in front of the church of Saint Donat and the Archbishop's Palace. It is a municipal square from the Roman era, built from the 1st century BC to the 3rd century AD, 45 by 90 metres in size. It represents a very developed example of the forum complex, and is one of the most important among the Adriatic ancient cities. The inscription with the name of Augustus' proconsul for Illyricum, Tamfil Vaale, carved on the well of the Forum, testifies that the complex construction was started as early as the second decade of the 1st century BC.

The forum is the name given to all main squares in the cities of the ancient Roman Empire, where the public life of the city unfolded. There was initially an about 2 metre high capitol on its south-western section, in the midst of which a temple dedicated to Jupiter, Juno and Minerva rises, while a monumental pillar is preserved to its north-western side, used in the Middle Ages as a "Pillar of Shame".

In the period of late antiquity, the foundations of Christian buildings were laid. They later developed into an episcopal complex with the basilica and annexes, and were joined by the rotunda in the Early Middle Ages, eventually destroying the complex of earlier erected buildings. In the course of history, the whole complex was reduced to rubble and the Kampa was built in its place, a medieval square with a Renaissance cistern.