A wetland reserve in the middle of the basalt desert that shouldn't exist — natural springs feed a marsh that draws migratory birds from Africa and Europe twice a year. Lawrence of Arabia based himself in Azraq's Umayyad-era fort during the 1917-18 Arab Revolt, and you can still walk through the same black basalt rooms he used. It's usually the last stop on the Desert Castles loop east of Amman.
Azraq is about 100 km (75-90 minutes) east of Amman, usually visited as part of a loop with the other Desert Castles (Qusir Amra, Qasr Al-Kharrana) rather than as a standalone trip.
Spring and autumn are best for the wetland reserve specifically, when migratory birds pass through in the largest numbers. The desert here is scorching in summer with almost no shade, so a cooler-season visit is genuinely more pleasant, not just prettier.
The wetland reserve is a small, easy boardwalk loop — comfortable shoes are enough, no hiking gear needed. It's a very different landscape from the rest of Jordan (flat black volcanic rock, "the black desert"), so don't expect sand dunes here; that's Wadi Rum, a few hours south.