The Site of al-Rasafeh, or ancient Sergiopolis, is located near Ar Raqqah, southwest of the Euphrates. The site lies in current day Syria.
Originally a military outpost for Assyrian troops built in the 9th century BC, al-Resafeh was fortified in Roman times as a desert outpost and station on the Strata Diocletiana. The city became quite wealthy, due to its location on prominent caravan routes.
During the Roma-Persian wars, the city was further fortified, with walls extending 1600ft in length and 1000ft in width. A fortress was also built at this time.
By the 4th century, Sergiopolis had become a pilgrimage site for Christians to venerate Saint Sergius, hence the renaming of the city. The city became a bishopric in 431 CE.
Archaeologically, the site is well preserved, with much of the walls and accompanying towers still standing.