Sideris
Sideris a river of Hyrcania, mentioned by Pliny (6.16. s. 18), which flowed into the Caspian sea. It cannot be now determined to which river he refers, but he states from it the Caspian sea was called the Hyrcanian.
From William Smith (ed.), Dictionary of Greek and Roman Geography. Text provided under a CC BY-SA license by Perseus Digital Library, http://www.perseus.tufts.edu, with funding from the National Endowment for the Humanities and Tufts University. Data accessed from https://github.com/PerseusDL/canonical-pdlrefwk/ on 17 October 2026.