Qasr Deir al-Kahf is a Roman fort located in northeastern Jordan, approximately 45 kilometres northeast of Qasr Azraq. Constructed in the 4th century CE along the Strata Diocletiana—a significant military road connecting Azraq and Bostra—the fort served primarily as a sentry post overseeing the surrounding arid landscapes. Built from black basalt, the square-shaped structure measures about 60 meters on each side and features corner towers, with additional interval towers on the north and west walls. The fort’s walls are approximately 1.5 meters thick and, in some sections, still stand up to 7.5 meters high. The original entrance was located on the east side, marked by a large basalt gate now embedded in the ground, while a later entrance was added on the west wall.

Over the centuries, Qasr Deir al-Kahf underwent modifications during the Byzantine and Islamic periods, reflecting its continued strategic importance. The fort’s design includes two-story rooms surrounding a central courtyard, which contains a cement-lined cistern, indicative of the Roman emphasis on water management in desert environments. Despite modern encroachments, the site remains one of the better-preserved examples of Roman military architecture in Jordan. Today, visitors can explore the ruins, gaining insights into the region’s historical significance and the architectural prowess of its ancient inhabitants.