Erzurum (Arm. Karin, Karnoy Kʿałakʿ; Gr. Theodosioupolis; Ar. Qālīqalā, Arzan al-Rūm, Arzarūm) is a city towards the north-eastern borders of present-day Turkey, on rising ground at the southeast corner of an extensive plain that is traversed by the Upper Euphrates (Turk. Kara Su), at a height of around 1,750 metres above sea level. In the early Middle Ages, Erzurum was for the Arabs a border base. From around the beginning of the fifth/eleventh century the city was the seat of a minor Turkish principality, that