East of Amman, there is an extensive desert plain where dozens of castles from the 7th to the 11th centuries are built. They all had various uses, from rest areas to military forts, like the Harranah Castle. They are especially well preserved. You can walk up and down throughout the grounds, and admire the magnificent views of the Jordanian desert from its rooftop. Like any monument of its wealth, it's full of local inscriptions and doodles.