ISNA | Mohammad Mahroumi: Zahhak Castle is perched on a hillside near Hashtroud, northwest Iran. The lonely castle served as a military stronghold during the Parthian era (247 BC – 224 CE). In the Persian legend, Zahhak is the name of an Arab king who conquered and ruled over ancient Iran. The story is recounted in the Shahnameh (Book of Kings), written by Iranian illustrious poet Ferdowsi.