Ajlun castle, situated on top of a mountain, was built in 1184, one of Saladin's generals to protect the iron mines and protection Aglona from the attacks of the Franks. Ajlun castle dominated the three main routes in the Jordan valley and protected the trade routes between Jordan and Syria. He was an important link in the chain of fortifications designed to protect against the crusaders, who for decades tried unsuccessfully to seize the castle and nearby village.

Originally the castle had four towers with loopholes in the thick walls with loopholes for archers and was surrounded by a moat of width 16 and a depth of 15 meters.

In 1215 the Mamluk Governor Aibak Ibn Abdullah extended the castle, adding another tower to the South-East corner and erecting a bridge, decorated with figures of doves, which can be seen today.

In XII century the castle was surrendered to the ruler of Aleppo and Damascus Salah ad-DIN Yusuf Ibn Ayyub. When it was restored the North-East tower. In 1260 the rebuilding of the castle were interrupted, and he fell under the onslaught of the Mongols. Soon, however, the Mamluk Sultan Baybars conquered the fortress and rebuilt it again.