The road to Ajloun, located 25 kilometers west of Jerash and 65 kilometers from Amman, winds through fertile green hillsides lined with olive groves. The main attraction in Ajloun is the stronghold of Qala'at al-Rabadh (Arabic for "Hilltop Castle"), a fine example of medieval Arab/Islamic military architecture. The castle was built between 1184-85 CE by the nephew of Salah Eddin al-Ayyubi (known in the West as Saladin), the great Muslim commander who waged a successful campaign to recover lands lost to the invading Crusaders.

Ajloun's strategic position commanding the Jordan Valley, as well as the three small valleys leading to it, made it an important link in the defensive chain against the Crusaders, who spent decades unsuccessfully trying to capture the castle and nearby village. The fortress is built upon the apex of the hill above Ajloun, and offers a breathtaking view of the surrounding countryside. On a clear day you can see the Dead Sea, the Jordan Valley, the West Bank, and Lake Tiberias (the Sea of Galilee).

The original fortress had four corner towers, with arrow slits and a 16-meter-wide moat. 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. During Mamluk times, Qala'at al-Rabadh was one in a network of beacons and pigeon posts that allowed messages to be transmitted from Baghdad to Cairo in only twelve hours!

Entrance is free to the castle, which is open seven days a week during daylight hours.