site located above Wadi Kafranja, one of three valleys between the two lakes which climb from the Jordan Valley up to the Transjordanian plateau (32°20′ N, 35°45′ E). ῾Ajlun has the best preserved Ayyubid mosque in Jordan. An inscription of al-Malik al-Mu῾azzam (RCEA 3970) demonstrates that it was founded in or before 1218–1227. The minaret was built under Baybars I In 1264 (RCEA 4528), and the doorway was repaired In 1332 (RCEA 5618).
῾Ajlun castle, called Qal῾at al-Rabaḍ (“citadel of the suburb”) after the suburb which grew up around it, occupies the last high point in the northern part of the valley. It was extensively restored by the Department of Antiquities of Transjordan In 1927–1929. The castle was founded In 1184–1145 by ῾Izz ad-Din Usama by order of Salah ad-Din (Saladin) to counter the threat posed by the Crusaders' Belvoir castle on the opposite side of the Jordan Valley. It may also have served to check Reynald de Châtillon, lord of Kerak, and to protect the region's rich iron ore deposits.
The nucleus of the castle was a four-towered keep on the site's highest point, flanked by two baileys on its eastern and southern sides. The main entrance lay beneath the southeast corner of the keep, protected by a machicoulis on two corbels (dismantled In 1927). The whole complex was surrounded by a deep rock-cut ditch.
The castle was extensively refortified in about 1214 by Aybak b. ῾Abd Allah, chamberlain (Ar., ustādh al-dār) to al-Malik al-Mu῾aẓẓam ῾Isa. He built the south tower to protect the reflex angle between the two baileys (RCEA 3746), added a ward to its east, constructed two outer gates (one decorated with zoomorphic carvings), and heightened much of the older structure.
Some restoration to the east wall was carried out in about 1253–1260 (RCEA 4463), before the castle was surrendered to the Mongols (In 1260). Crude repairs to the keep and the southwest corner are postmedieval. The castle was still inhabited when J. L. Burckhardt visited it In 1812, and Ibrahim Pasha installed a small Egyptian garrison there In 1831–1841.
- Johns, C. N. “Medieval ῾Ajlūn: The Castle.” Quarterly of the Department of Antiquities of Palestine 1 (1932): 21–33. Good account of the castle's history and construction.
- Répertoire chronologique d'épigraphie arabe (RCEA). 18 vols. to date. edited by Étienne Combe, Jean Sauvaget, and Gaston Wiet. Cairo, 1931– . Standard collection of Arabic epigraphy.