Syria is littered with ancient Roman sites and one ruin worth a look is that of the Roman city at Resafa. Originally a military camp built by the Assyrians in the 9th century BC it was in a handy position on the caravan routes, so flourished and later became a city. The Roman Emperor Justinian fortified the city as it was caught between the Romans and the Persians during their wars.
At one stage the city was known as Sergiopolis as it was named after a Saint. It was a pilgrimage for people visiting the grave of Saint Sergius, a martyred Christian soldier. A church was built to mark his grave and it became an important pilgrimage center in Byzantine period.
There are still substantial sections of the city walls to be seen and some of the main buildings. Most impressive are the underground water cisterns which were needed because the city had no spring or running water. The massive underground cisterns were used to collect water from the winter and spring rains.