Calpas or Kalpas, also known as Calpe or Kalpe ( grc, Κάλπη) was a river of ancient Bithynia draining into the Pontus Euxinus, between the

Psilis The Psilis ( grc, Ψίλις) or Psillis (Ψίλλις) was a river of ancient Bithynia that drained to the Pontus Euxinus The Black Sea is a marginal mediterranean sea of the Atlantic Ocean lying between Europe and Asia, east of the Balka ...

, from which it is 210 stadia distant, and the Sangarius River. Near its mouth was the port of Calpe, through which Xenophon passed on his retreat with the Ten Thousand. Xenophon describes it as about halfway between

Byzantium Byzantium () or Byzantion ( grc, Βυζάντιον) was an ancient Greek city in classical antiquity that became known as Constantinople in late antiquity and Istanbul today. The Greek name ''Byzantion'' and its Latinization ''Byzantium'' cont ...

and Heraclea Pontica on a promontory, part which projects into the sea is an abrupt precipice. The neck which connects the promontory with the mainland is only wide. The port is under the rock to the west, and has a beach; and close to the sea there is a source of fresh water. The place is minutely described by Xenophon. Apollonius of Rhodes calls the river "deep flowing". It is identified with the modern Ilaflı Dere.

References

Geography of Bithynia Rivers of Turkey Kocaeli Province Ancient Greek geography {{Turkey-river-stub