Saimbeyli, alternatively known as Hadjin (Հաճըն), is a town and district of Adana Province, Turkey. Its area is 989 km2, and its population is 13,621 (2022). The town is located at the Taurus mountains of Cilicia region, 157 km north of the city of Adana. Saimbeyli is on the Göksu river (one of the sources of the Seyhan, in a valley between the forested mountains of Dibek and Bakır. There is a pass through the mountains from here to Kayseri and the valley is watered by many mountain streams. The area probably has the foundations of Hittite settlements. There is no evidence at present that it was occupied in the Roman period, but it seems likely. The fortress of Saimbeyli may be the medieval Badimon or perhaps the castle of Berdus, which appears on the Coronation List of King Levon I of Cilician Armenia in A.D. 1198/99. This fortress, which guards the strategic road between Kayseri to the north and the Rubenid castle of Vahka to the south, stands on an outcrop at the junction of two valleys and two tributaries of the Seyhan River. The plan and masonry of Saimbeyli’s castle are identical to the military architecture in the Armenian Kingdom of Cilicia and undoubtedly date from the mid-12th century to the 13th century. Two large round towers with embrasured loopholes (shooting ports) guard the entrance at the northwest, while the remainder of the circuit is protected by steep cliffs below and three rounded salients. In the lower level of the salient in the east wall is the apse for a chapel. A well-preserved vaulted cistern is located near the southwest side of the ward. The exterior masonry consists of ashlar blocks with a rusticated facing. There is evidence of repair, perhaps into early modern times. Opposite and below the fortress are the substantial remains of ecclesiastical and civilian architecture, which date from the 14th through the 19th century. The monastic complex dedicated to St. James is perched on the side of a tall hill at the northwest end of the village.