Ajlun is a small town in the highlands of northern Jordan, set among forested hills that are unusually green for the region. It sits about 75 km north of Amman and makes an easy half-day or full-day excursion from Jerash, which lies just to the east. Most visitors combine the two in a single day.
The main draw is Ajlun Castle (Qalat er-Rabad), a 12th-century Ayyubid fortress built by one of Saladin's generals to defend against Crusader incursions. The castle commands a sweeping view over the Jordan Valley and three wadis — on a clear day you can see all the way to Palestine. It remains one of the best-preserved Islamic military fortresses in the Levant, and the small archaeological museum inside it adds useful context.
Beyond the castle, the Ajlun Nature Reserve protects a stretch of oak, carob, and pistachio woodland — habitat rare in the Middle East. The RSCN (Royal Society for the Conservation of Nature) maintains five marked trails here, ranging from a short 1 km loop to the full-day Prophet's Trail, which ends at Tell Mar Elias, a Byzantine hilltop site associated with the Prophet Elijah. The reserve has overnight bungalows if you want to stay. Olive grove walks through the surrounding hills — especially during harvest season in October — are a gentler alternative. Nearby Anjara has an old church worth a look.