CAISTER, or CAYSTRUS, in Ancient Geography, a river of Ionia, whose mouth Ptolemy places between Colophon and Ephesus; commended by the poets for its swans, which it had in great numbers. Its source was in the Montes Gilbani, (Pliny). Caystrius Campus was a part of the territory of Ephesus. Campi Caystriani of Lydia were plains lying in the middle between the inland parts and Mount Tmolus.