Damascus citadel is a fortress was established in the Middle Ages, it is one of the most important military art and architecture landmarks in Syria backing to the Ayyubid period, it has been included in the UNESCO list of World Heritage Sites in 1979 AD. 
The citadel is located in the northwest corner of the old city of Damascus, Damascus Citadel was built on level ground at the same level the rest of the city of Damascus, unlike most Arab castles in the Middle Ages which was located on the hills prominent peaks. The location of the castle ensures control and monitoring of the Barada River, which flows from the northern side of the castle, as the river site also provides protection of the castle against any attack from this side, flowing Oaqrabana River down the north wall, which is one of the branches of the river Barada , it also provides additional protection for the citadel, as it fills the dry ditches on the sides of the citadel.
There is also another branch of the Barada River, is the Banias River, which passes under the citadel to the city of Damascus. 
The construction of hydraulic structures inside the castle, which control the flow of water below to Damascus is made in the era of king Aladel Abu Baker bin Ayub.