Editing Bithynia (section)

=== Byzantine province ===
[[File:Istanbul_Gate,_Iznik,_Turkey_(37659560615).jpg|thumb|250px|The Constantinople Gate in [[Nicaea]]]]

Under the [[Byzantine Empire]], Bithynia was again divided into two provinces, separated by the [[Sakarya River|Sangarius]]. Only the area to the west of the river retained the name of Bithynia.{{sfn|Chisholm|1911|p=13}}

Bithynia attracted much attention because of its roads and its strategic position between the frontiers of the [[Danube]] in the north and the [[Euphrates]] in the south-east. To secure communications with the [[Praetorian prefecture of the East|eastern provinces]], the monumental [[Sangarius Bridge|bridge across the river Sangarius]] was constructed around 562. Troops frequently wintered at Nicomedia.

During this time, the most important cities in Bithynia were [[Nicomedia]], founded by Nicomedes, and [[Nicaea]]. The two had a long rivalry with each other over which city held the rank of capital.