The fortress is built upon the apex of the hill above 'Ajloun, and offers a breathtaking view of the surrounding countryside. It was enlarged in 1214-15 CE by the Mamluk officer Aibak ibn Abdullah, who added a new tower in the southeast corner and constructed the main one. In 1229, the castle fell to the Emirate of Karak. In 1260, it was largely destroyed by the Mongol invaders, but was reconquered and rebuilt almost immediately by the Mamluk Sultan Baybars. The southwest tower was constructed at that time.
Entrance is free to the castle, which is open seven days a week during daylight hours.
Irbid's importance as a trading center with Haifa ended in 1948, but in recent years it has gained importance as the industrial center and administrative capital of the north. The city has a good selection of restaurants, a number of banks and hotels, and the campus of Yarmouk University. Artifacts and graves in the area show that Irbid has been inhabited since the Bronze Age. Scholars have debated whether Irbid is the biblical site of Beth Arbel, or Beit Arbil in Arabic. Under Roman rule, the city was renamed Arbila.