Juliopolis or Ioulioupolis (Greek: Ἰουλιούπολις), occasionally also Heliopolis (Ἡλιούπολις),[1] was an ancient and medieval city and episcopal see in Anatolia (modern Turkey). In later Byzantine times, it also bore the name Basilaion (Βασιλαίον). Various authors assign it to the regions of Galatia, Bithynia, and Paphlagonia. Now, it is in the province of Ankara, Nallıhan.