Rumkale Located about 50 km from the city center of Şanlıurfa on the River Euphrates is the ancient fort of Rumkale, which is one of the most significant places in the region. The fort has its roots in Assyrian times, but its present structure is predominantly Hellenistic and Roman. According to legend, John, one of Jesus' disciples, resided there during Roman times and played a significant role in the spread of Christianity. Throughout the Middle Ages, various Byzantine and Armenian warlords occupied Rumkale, which was also home to an Armenian bishop from the 12th century. In 1179, a synod was held in Rumkale to attempt to reach a compromise between Greeks and Armenians. From 1203 to 1293, it was the religious center of the Armenian Church until it was captured by Muslim Mamluks in 1293. It was then controlled by the Ottomans. Rumkale is one of the most important Christian historic sites, and its architectural ruins span from the Late Roman to the Middle Ages. Visitors can explore an area of 3500 m2 that includes columns and bushes, the 13th-century Barsavma Monastery, Saint Nerses Church (1175), water cisterns, a spiral well, and an 8-meter wide and 75-meter deep ditch. In the 11th century, Rumkale's significance stemmed from the story that John, one of Jesus' apostles, lived there during the Roman era and produced copies of Bibles in a hidden room within the rocks. Additionally, during the time of Nerses, the poet saint, who gathered all ambassadors from across the empire for a national movement to unite sects, Rumkale Castle became a crucial site. Once a prosperous city situated on a peninsula created by the reservoir of Birecik Dam, Rumkale can now be accessed by boat from the nearby site of Zeugma or from the town of Halfeti, which is within Şanlıurfa's Halfeti district.