Palmyra, Qasr al-Heir ash-Sharqi
If you want to visit the desert castles, don't miss Qasr al-Heir ash-Sharqi, located about 120 Km Northeast from Palmyra.
The fort was built during the Umayyad period as a military outpost. It consists of an open courtyard surrounded by a wall. In order to access its interior you have to pay for an entrance fee.