Octavian built the military harbor of Classis at Ravenna, and the city remained an important seaport on the Adriatic until the early Middle Ages.

In 401, Western Roman emperor Honorius moved his court from Mediolanum to Ravenna; it then served as capital of the empire for most of the 5th century.

After a brief Lombard control, Ravenna came under the authority of the Papacy and, save for minor interruptions, remained part of the Papal States until the mid-19th century when it was incorporated into the newly unified Kingdom of Italy.

It is known for its well-preserved late Roman and Byzantine architecture, with eight buildings comprising the UNESCO World Heritage Site "Early Christian Monuments of Ravenna".

Ravenna consisted of houses built on piles on a series of small islands in a marshy lagoon – a situation similar to Venice several centuries later.

[16] The transfer was made partly for defensive purposes: Ravenna was surrounded by swamps and marshes, and was perceived to be easily defensible (although in fact the city fell to opposing forces numerous times in its history); it is also likely that the move to Ravenna was due to the city's port and good sea-borne connections to the Eastern Roman Empire.

In 409, King Alaric I of the Visigoths simply bypassed Ravenna, and went on to sack Rome in 410 and to take Galla Placidia, daughter of Emperor Theodosius I, hostage.

After many vicissitudes, Galla Placidia returned to Ravenna with her son, Emperor Valentinian III, due to the support of her nephew Theodosius II.

Ravenna enjoyed a period of peace, during which time the Christian religion was favoured by the imperial court, and the city gained some of its most famous monuments, including the Orthodox Baptistry, the misnamed Mausoleum of Galla Placidia (she was not actually buried there), and San Giovanni Evangelista.

Theodoric, following his imperial predecessors, also built many splendid buildings in and around Ravenna, including his palace church Sant'Apollinare Nuovo, an Arian cathedral (now Santo Spirito) and Baptistery, and his own Mausoleum just outside the walls.

Nevertheless, the archbishop of Ravenna held the second place in Italy after the pope, and played an important role in many theological controversies during this period.

Pope Adrian I authorized Charlemagne to take away anything from Ravenna that he liked, and an unknown quantity of Roman columns, mosaics, statues, and other portable items were taken north to enrich his capital of Aachen.

After a short period under an Imperial vicar, Ravenna was returned to the Papal States in 1248 and again to the Traversari until, in 1275, the Da Polenta established their long-lasting seigniory.

The last of the Da Polenta, Ostasio III, was ousted by the Republic of Venice in February 1441, and the city was annexed to the Venetian territories in the Treaty of Cremona.

Fifty-two Allied bombing raids during the course of the Second World War had taken their toll, destroying some of Ravenna's noteworthy, unequalled early Christian art.

[19] On 5 November 1944 troops of 4th Princess Louise Dragoon Guards, 5th Canadian Armoured Division and the British 27th Lancers entered and liberated Ravenna.

These are Other historic sites include: The city annually hosts the Ravenna Festival, one of Italy's prominent classical music gatherings.

Ravenna railway station has direct Trenitalia service to Bologna, Ferrara, Lecce, Milan, Parma, Rimini, and Verona.