Ermoupolis, Hermoupolis (both: ĕrmōˈpôlĭs) [key], or Síros sēˈrôs, city (1991 pop. 13,030), capital of Cyclades prefecture, SE Greece, on the east coast of Síros island. It is the chief city of the Cyclades and a major Aegean port and commercial center. Ship repair, ironworks, tanning, and textiles are significant industries. It grew rapidly after being founded (c.1820) by refugees from Khíos and Psará islands.