Semystra

Semystra (Ancient Greek: Σημύστρα, romanized: Sēmústra) or Semestra was a nymph in Greek mythology who was associated with foundational legends of the city of Byzantium (present-day Istanbul). There was a sanctuary of the same name dedicated to her near the city, at the head of the Golden Horn, at the confluence of the rivers Kydaros and Barbyses.