Limes Arabicus: Roman Empire's desert frontier from Gulf of Aqaba to northern Syria
AMMAN — The Limes Arabicus was a desert frontier established by the Roman Empire, and stretched from the Gulf of Aqaba and ancient Ayla all the way to northern Syria, with 1500 km at its greatest extent. Several fortresses and watch towers were used to prevent attacks from nomadic raiders and military moves of Parthians and troops of Sassanid Empire.
Source: jordantimes.com