'Roman Castle'; Armenian: Հռոմկլա, romanized: Hromgla) is a ruined fortress on the Euphrates, located in the province of Gaziantep and 50 km west of Şanlıurfa.

Although Rumkale is sometimes linked with places mentioned in ancient sources, the foundations of the structure can be traced back to the Byzantine rule the earliest, when the fortress was the seat of a Syriac Orthodox bishopric.

Sometime between 1148 and 1150, Catholicos Grigor III Pahlavuni purchased the fortress making it the headquarters of the Armenian Apostolic Church, although it continued to house Syriac Orthodox and Catholic representatives.

[2] Although the site was known as Rumkale and its variations throughout the entirety of its history from the medieval to late Ottoman period, it was renamed to Qal'at al-Muslimin following its capture by the Mamluk Sultanate in 1292.

[2] The site likely evolved into a settlement in the 11th century with the immigration of Armenians from the north as the Byzantine forces displaced a significant population from their lands.

In 1179, a synod of 33 Armenian bishops took place in Hromgla came up with a compromise and sent a profession of faith to Byzantine Emperor Manuel I Komnenos, but he died in September 1180 before it reached him.

[13] The site became an important center for manuscript production, reaching its artistic peak under the Catholicos Constantine I who employed Toros Roslin, whose stylistic and iconographic innovations had profound influence on subsequent generations of Armenian art.

[11] By 1268, Hromgla was isolated from the remainder of the Armenian kingdom of Cilicia and was attacked by a force of Mamluks of Egypt, which destroyed the town while it was unable to conquer the citadel.

[15] In 1292, the castle was captured following a protracted siege by the Mamluks under al-Ashraf and its garrison massacred while the clergy and other population were made prisoners or enslaved.

Although the Ottoman forces camped 25 km west of Rumkale near the Merziman Stream, they did not lay siege to the town and began advancing towards Ayntab.

[22] In 1517, Rumkale became the center of its namesake sanjak with Omer Beg-oghlu Idris as its sanjak-bey as part of the new Damascus-based Vilayet-i Arab (lit.

[14] Following the 1831 rebellion led by Bekirzade Mehmed Bey, the voivode (tax-collector, warlord) of Rumkale, the Ottoman government decreed the depopulation of the town and the destruction of the homes to prevent the fortress from harboring any future rebels.

[26] The remaining few intact buildings were bombarded by Ibrahim Pasha in 1832[27] during the Egyptian–Ottoman War, which forced the residents to relocate to the village of Kasaba, while influential families moved to the town of Halfeti on the opposite (eastern) side of the Euphrates or the city of Aintab in the west.

Hizir Ilyas Mosque differs from the rest as it was not found in any archival records but is identified in a photo dated back to late 19th century.

Historian Muhsin Soyudoğan points out that Zamahiya, the transliteration put forward by Yılmaz and Karadeniz in prior publications, is a result of the misreading of the shaddah, Arabic diacritic equivalent of double consonants, as a dot above the first letter, rāʾ, (ر‎) so that it was zāy (ز‎).

[35] The fortress, now situated across a peninsula created by the reservoir of Birecik Dam and within the administrative boundaries of Gaziantep's Nizip district, is currently accessible by boat either from the neighboring site of Zeugma or from the town of Halfeti.