Its location over some sandy hills, in an interior position than the actual coast-line, directly in front of a wide inner lagoon where the sea met the hydrographic system constituted by the Po and the Reno rivers and impostato sul Padenna e sugli affluenti Flumisello e Lamisa, favoured the early occupation of the area (between the VI and the IV cent. B.C), mainly by the Umbrian and Etruscan populations, with an influence of the Venetian and Greek components. In this proto-urban period, during the IV cent. B.C. Ravenna was not characterised by a regular planning, because of its geo-topographic situation and of the dominance of waters. Nevertheless it was already a real harbour within the endo-lagoon commercial system, in connection with the centres of Adria and Spina.

The romanisation of the town can be dated to the III cent. B.C. It was not due to a specific process of colonisation but it can be explained by the efficiency of its harbour and the presence, behind the town, of some wide lagoons suitable also for large boats. To the same period can be attributed the construction of a defensive ring of walls surrounding the so-called “square” Ravenna, characterised by a quadrangular perimeter and an orthogonal street and water drain structure. 

Augustus’ decision to establish the seat of the Imperial fleet in Ravenna for the control of the whole Eastern Mediterranean basin, thus giving rise to the development of the town, was strictly connected to the peculiarity of the place and the hugeness of its lagoon harbour, that could host more than 250 armed triremes. These features had already been used formerly on several occasions, the most important of which was represented by Caesar’s preparations for war in Ravenna before the passage on the Rubicon.

Interments, river deposits, subsidence and the building needs of a town characterised by a millenarian history, which was chosen several times as a capital city, make the “reading” of Ravenna urban tissue very complex, especially for the late-republican and proto-imperial period, which are still less known. More information are available concerning the monumentalisation, following the establishment of the military fleet, carried out by Emperors Angustus and Claudius.

Among the most important works are the construction of the harbour and its connection with the sea by an artificial channel – along which Classe, one of the two suburbs of Ravenna together with Caesarea, much less important than the other, formed – the opening of the Fossa Augusta (an artificial water-course that connected Ravenna with the Venetian lagoon), the building of the Porta Aurea (honorary arch, which was subsequently included in the ring of walls) as a new urban entrance through the harbour, the diversion through the town of the via Popilia, which originally run outside the urban centre.

Several public buildings are cited by the ancient sources (a temple dedicated to Neptune, the Basilica Herculis, a circus, a gladiatorial school, some thermal buildings, the Caesareum, and an amphitheatre in Classe) but only one temple, which could be identified as the Capitolium, was uncovered under the church of S. Domenico. The construction of the aqueduct, of which some pillar are still present along the river-bed of the Montone south of the city, belongs to the Imperial period, under Trajan.

The private buildings are better known thanks to the investigation of several houses, often furnished with mosaic floorings: the Adrian domus of D’Azeglio street; the domus under Santa Croce, the domus between S. Vitale and Galla Placidia Mausoleum, the domus of the Banca Popolare, the domus of the Cassa di Risparmio.

After a period of decline in the IV cent. A.D., after the retreat of the fleet and the progressive interment of the harbour, at the beginning of the V cent. Honorius orders to move the capital from Milan to Ravenna, which he considered to be more easily defensible since it was surrounded by swamps and could only be reached by the sea. This event marks the beginning of a new “renaissance” for the town, which was even more favoured by the twenty-five lasting regency of Gallia Placidia.

It is the rising of the Imperial palaces and the first Christian religious buildings, among which the Ursiana basilica, the Neonian baptistery, the bishop’s palace, some important churches and the famous Mausoleum of Galla Placidia. The Fossa Augusta is closed and the main street in the town is built over it (Plateia Maior). The Imperial quarter occupies the new areas beyond the Fossa, formerly used as cemeteries.

Ravenna lives another period of extraordinary splendour when Theodoric conquers the town after the defeat of Odoacer, at the end of the VI cent. A.D. He realizes a series of works of restoration concerning Trajan’s aqueduct, the road network and the harbour, realised from the transformation of the ancient Roman harbour channel. The construction of the real palace - to which the actual church of S. Apollinaris The New is connected as a chapel - starts. North of the town a new quarter develops, where different buildings are erected dedicated to the Arian cult professed by Theodoric, such as the Cathedral and the Baptistery. The Gothic king orders also the construction of a Mausoleum out of the town ring of walls in the same area of the necropolis used by his people.

In the second half of the VI cent., when Justinian reaches the power and the Eastern and Western Empires are unified after the Greek-gothic war, Ravenna undergoes its last period of urban magnificence after having entered the Byzantine sphere of action. The presence of influential personages such as Iulianus Argentarius and the engagement of Ravenna’s church represent the propulsive elements of a new building phase which saw several important works realised such as S. Vitale’ church, the basilica of S. Apollinare in Classe, as well as the restoration of the Imperial palaces.