Qasr al-Hallabat is located just off the main road about 30 kilometers east into the desert from Zarqa. It was originally a Roman fort built during the reign of Caracalla (198-217 CE) to defend against raiding desert tribes.
There is evidence that, before Caracalla, Trajan had established a post there on the remains of a Nabatean settlement. During the seventh century CE, the site became a monastery, and the Umayyads then fortified it and decorated it with ornate frescoes and decorative carvings. Two kilometers past Qasr al-Hallabat, heading east, are ruins of the main bathing complex known as Hammam al-Sarah. The baths were once adorned with marble and lavish mosaics. Today, you can still see the channels that were used for hot water and steam.