Stretching east from Amman is a desert region bewildering in its size and ruthless climate, a place of sand and barren basalt landscapes which bear witness to ancient glories. The Ummayed Caliphs of the early Islamic era, out of socio-economic and political concerns, built a string of palaces, hunting lodges, baths, meeting places, caravansaries and fortresses in the farthest corners of the desert. Known collectively as the Desert Castles, the constructions demonstrate the best of early Islamic Architectural ingenuity.

Located just 2 km from Qasr Azraq, Ain Es-Sil is one of the examples offering a different perspective on Desert Castles. Lying by the pine trees it was never used as a palace but rather as a farming estate with a bathing complex attached. This complex was built by the Umayyads, possibly over the existing fortifications of a Roman building.

The main building is asymmetric, no more than about 17 meters along each of the four walls. It was constructed, like all the other structures at the site, using circular-shaped bricks of different dimensions made of black basalt. The entrance to the east wall leads to a courtyard with seven rooms around it.

At the west wall are the remains of a small bathhouse which, like those at Amra, would have had a changing room as well as hot and cold baths. The hot bath would have had a hypocaust – the Roman heating system in which hot air was circulated under the floor and between double walls – similar to that at Amra although not nearly as elaborate. A couple of olive presses were also discovered during a series of excavations in 1984.