Ajlun west of Jerash, a fine example of Arab-Islamic military architecture, the Castle was built in the 12th century by Ossama ibn Munqidh a nephew of Saladin who defeated the Crusaders in 1189. It was built to develop and control the iron mines of Ajlun and to protect the trade and communications between south Syria and Jordan. From the hill top the visitor can enjoy a splendid view over the Jordan Valley.