The desert between Amman and Azraq is littered with the remains of old castles. Most were retreats for kings and nobles, others were defensive fortifications. They are an important part of Jordan's heritage and definitely worth a visit. Tour groups regularly go to each site. You also may want to rent a car or hire a taxi for the day if you want more freedom to explore.
Located about 30km east of Amman along the main eastern road, it was originally built in the third century by the Romans to defend against desert raiders. The fortification there today dates back to the Umayyad period. It's a lot of fun to explore the old fort. Like most of Jordan's archaeological remains, visitors are free to go where they please.
Further down the road to Azraq, Quseir Amra is one of three UNESCO World Heritage Sites in Jordan. The oasis here was originally a rest stop for caravans. In the early eighth century, the Umayyad caliph Walid I built a retreat that still stands. The highlight is the frescoes in the bathhouse that display scenes from the zodiac. The entire complex is remarkably well preserved, though it's not very large.
Just north of the town of Azraq, Azraq Castle was first constructed in the third century by the Romans. The modern fortress dates back to the Mamluks in the thirteenth century. It was also used by the Ottomans. Azraq Castle's main claim to fame is as Lawrence of Arabia's winter 1917 headquarters during the Arab Revolt. The castle is distinguished by its black basalt rocks. Once again, it's fun to explore all of the nooks and crannies.
Quseir Al Hallabat
Northeast of Zarqa, this castle was built during the reign of the Roman Emperor Caracalla in the third century AD. The Umayyad caliph Walid II converted it into a pleasure palace. It is not as well preserved as the other sites, and archaeologists are currently undertaking a renovation project. It's located in the village of Hallabat and is accessible by bus.
This is but a small sampling of the region's many castles. If you want to see any more, you'll likely need more than one day to do so, as their locations are more remote. Accommodations, albeit not particularly comfortable ones, can be found in Azraq.
Al Azraq Hotel and Resthouse
Telephone: +962 6 383 4006