According to Yasna, 19, 18, the zarathushtrotema, or supreme head of the Zoroastrian priesthood, had at a later (Sasanian) time, his residence in Ragha.
His home appears to have been at Samosata.2 By the beginning of the 4th century much progress had been made with the organization of the Christian church not only within the Roman district of Mesopotamia, but also to the east and south-east within the Sasanian Empire, round such centres as Seleucia-Ctesiphon on the Tigris (near Baghdad), Karka de-Beth Selokh (modern Kerkuk) and Beth Lapat or Gundeshabhor (in the modern province of Luristan).
One result of this and later persecutions of the same kind has been to enrich Syriac literature with a long series of Acts of Persian Martyrs, which, although in their existing form intermixed with much legendary matter, nevertheless throw valuable light on the history and geography of western Persia under Sasanian rule.