Prusias ad Hypium

Prusias ad Hypium was a city in the late Roman province of Honorias and a bishopric that was a suffragan of Claudiopolis in Honoriade. It was near present-day Düzce, Turkey.

Memnon of Heraclea says that King Prusias I of Bithynia (237-192 B.C.) captured from the Heracleans the town of Kieros, united it to his dominions and changed its name to Prusias.Pliny and Ptolemy merely mention it, one below Mt. Hypius, the other near the River Hypius or Milan-Sou.

Several of its bishops are known:

It is not known when this see disappeared; it still existed in the tenth century.

...
Wikipedia