The Qal'at al-Rum (Arabic: قلعة الروم) was a powerful fortress on the river Euphrates, 50 km west of Şanlıurfa. It is called Hromkla in Kurdish, Rumkale in Turkish, Հռոմկլա (Hromkla) in Armenian,; the name means "Roman Castle (by extension also Byzantine)" in all cases.
Its strategic location was already known to the Assyrians, although the present structure is largely Byzantine and Armenian in origin, with extensive rebuilding following the Mamluk conquest. After the Byzantine withdrawal from the region in the later eleventh century, it was held by Armenian princes until it was absorbed into the Frankish county of Edessa in the years following the First Crusade, and when it was known as 'Ranculat'. From 1151 until 1292 Hromkla served as the seat of the supreme head (catholicos) of the Armenian church[1]. In 1292 it was captured by the Mamluks of Egypt following a protracted siege, when it was officially renamed 'Qal'at al-Muslimin', a name which, however, seems not to have stuck.
The fortress, now situated across a peninsula created by the reservoir of Birecik Dam and within the administrative boundaries of Şanlıurfa's Halfeti district, is currently accessible by boat either from the neighboring site of Zeugma or from the town of Halfeti. As of September 2011, it was not possible to land at the site; there seems to be extensive (re)building under way inside the fortress and on the external walls, and this seems to be being undertaken in an unsympathetic way. Much of the surrounding work of the fortress, along with local villages and farmland, has been flooded; it is not clear how much of the entrance way up from the western side remains undamaged by the rising waters.
Angus Stewart (2006), 'Hromgla', in Alan V. Murray (ed.), "The Crusades: An Encyclopaedia", II, p. 607. ABC-CLIO, Inc., ISBN 1576078620.