The walls stand up to 20 feet tall. It was built at the start of the 4th century AD, as part of defensive works for a limes Arabicus, and held a cavalry unit of perhaps 120-150 men. The building inscription survives:Optimis maximisque principibus nostris Caio AurelioValerio Diocletiano Pio Felici Invicto Augusto etMarco Aurelio Valerio Maximiano Pio Felici Invicto Augusto etFlavio Valerio Constantio et Galerio Valerio Maximianonobilissimis Caesaribus Castra Praetorii Mobeni fossamentisAurelius Asclepiades praeses provinciae Arabiaeperfici curavit.Which tells us that the fort was called Mobene, and was constructed by the Praeses of the province of Arabia, a chap named Aurelius Asclepiades,...