The urban topography of the Milesian (7th c. BC) colony of Istros on the western shore of the Black Sea, is a very fertile research topic, as there is a large quantity of old data that has not been thoroughly analyzed and put into a more general context. And this information is at the same time important and difficult to interpret, as it pertains to very different periods, starting with the Archaic period and ending with the Late Roman and Early Byzantine.

A series of recent multidisciplinary investigations, as well as classical excavations, made it possible to study a larger area around the Basilica with Crypt Sector in Istros. The results concern the local road system and the manner in which it was articulated with the Late Roman urban tissue, depending on the newer and older urban focal points.

The presentation's primary focus is the evolution of an open area conventionally called the Main Square (located immediately in front of the most important access way inside the Late Roman city walls) from one of the city's Est-West streets to what we believe was the Late Roman city's main public space. The reason for this choice is that recent discoveries in this area made us question and reconsider a series of sometimes inherited preconceptions concerning this obviously major focal point in the layout of the city's Late Roman urban plan.

In order to further clarify the role that the so-called Main Square played in the functioning of the city, we considered a series of research questions: when, how and why was this space created?

In the attempt to answer these questions, we first collected data from old excavations, which were not necessarily analyzed together in previous studies. We then analyzed new data from recent research projects that combine classical archaeological excavations with geophysical (magnetometric and GPR) and aero photogrammetry data, considering the place's physical topography, as well as its place in the urbanitas.

This approach allowed us to follow the area's evolution that saw, through the use and enhancement of the topographic features, as well as through changes in the urban grid and the raising and elimination of certain buildings, the creation of the new, focal point of the Late Roman city, a place of religious memory and one that played an important role in the local identity-building process.