Adıyaman is a town in present-day southeastern Turkey, in the Euphrates basin south of and beneath the Taurus range, located on the site of the ancient settlement of Pordonnium (Lat.), which probably betrays a local name from which Adıyaman is also derived. In the ʿAbbāsid period, it was known as Ḥiṣn Manṣūr, one of the thughūr fortresses built by Hārūn al-Rashīd (r. 170-93/786-809), which replaced Perrhē as the principal local settlement, whose remains lie at Pirun, four kilometres to the northeast. Pordonnium and Perrhē both