The answer is Ravenna. The city is on a lowland plain close to the union of the Ronco and Montone rivers, 6 miles (10 km) inner from the Adriatic Sea, with which it is linked by a canal. Ravenna was a significant part in history as the principal of the Western Roman Kingdom in the 5th century AD and later (6th–8th century) of Ostrogothic and Byzantine Italy.