The Phanaroea plain (Φανάροια), the modern Erbaa Plain, is a plain lying mostly in the Erbaa district of Tokat Province in the Black Sea region of Turkey. It runs east-west for about 60 kilometres (37 mi), along the Kelkit River in a valley created by the North Anatolian Fault. It has a maximum width of 8 kilometres (5.0 mi). The Yeşilırmak runs along its western edge and is joined by the Kelkit in the northwest corner of the plain. Its altitude ranges from about 200–260 m. The Niksar plain to the east, at 260–300 m altitude, continues the Erbaa plain, and is generally considered part of the Phanaroea.