Elis or Eleia (Greek, Modern: Ήλιδα Ilida, Ancient: Ēlis; Doric: Alis; Elean: Walis, ethnonym: Ϝαλειοι) is an ancient district that corresponds to the modern Elis regional unit. Elis is in southern Greece on the Peloponnesos peninsula, bounded on the north by Achaea, east by Arcadia, south by Messenia, and west by the Ionian Sea. Over the course of the archaic and classical periods, the polis of Elis controlled much of the region of Elis, most probably through unequal treaties with other cities, which acquired perioikic status. Thus the city-state of Elis was formed.