Tetrapyrgium (Qseir es-Seileh), a Late Roman Frontier Fort

Tetrapyrgium, whose Greek name means “four towers”, is a small Late Roman frontier fort. It lies south of the legionary city of Sura and 16 kilometres north of Resafa, on the military road known as the Strata Diocletiana. The fort measures about 38 by 37 metres, with quarter-circle towers at its four corners, and it held a garrison of 65-70 soldiers. It is the only small frontier fort in eastern Syria whose plan, measurements and dating are documented by excavation. What remains on the ground today, however, is not known.

Where it is

About 12500 metres — eight Roman miles — south of Sura. The fort sits on a terrace on a north-facing slope and could be seen from far across the plain; it had a visual signalling link with both Sura and Resafa. Its local name, as recorded by Western researchers, is Qseir es-Seileh. The original Arabic spelling of that name could not be confirmed in an Arabic source.

What the fort was like

The plan is a slightly skewed square. The single gate is in the middle of the west side, and the approach road is more than three metres wide and paved with stone. The east wall is of mudbrick and survives to more than four metres high; its lower part is a double shell of Roman concrete, a mortared rubble fill. Rooms line the inner courtyard.

Beside the fort was a civilian settlement, or vicus, of about 230 by 250 metres. In the first half of the 6th century it was enclosed by a wall about two metres thick with some ten towers. Water came from cisterns: a pear-shaped one 120 metres south-east of the fort and three 250 metres to the north. The necropolis east of the vicus covers at least 18800 square metres and is full of pits dug by tomb robbers.

When it was in use

The earliest Roman finds on the site date from the 1st century AD, and there are also finds from the governorship of Marcus Ulpius Traianus. According to Michaela Konrad, who led the excavation, the fort was built after 324. The coins stop in 518/527 and the pottery in 580, so the fort was abandoned around 580.

Around 720 a short-lived monastery, dated by coins of the caliph Hisham, was set up and reused the fort’s stones. Traces of occupation end shortly after 750.

Who found it and who dug it

An anonymous pilgrim from Piacenza, writing around 570, mentions a “civitas Tetrapyrgium”. The Czech scholar Alois Musil identified the sand-covered ruin of Qseir es-Seileh with that name between 1908 and 1915. Dussaud studied the site in 1929, followed by Poidebard and Mouterde in 1930-1931. The Damascus branch of the German Archaeological Institute made a test trench in 1990 and excavated in 1992-1996 under Michaela Konrad and Markus Gschwind. The results are in Konrad’s 2001 book on the Late Roman frontier in Syria and in her article on Umayyad pottery from the same year.

Can you visit today

This could not be confirmed. Tomb robbing was threatening the site, and no source was found showing what remains on the surface after 2011. The site’s coordinates also rest on a single source, so this page has no map. If you plan to go, ask locally about the route and the state of the site in Raqqa or on the Resafa road.

What not to miss

How small the fort is. Each side is 38 metres — about the size of a courtyard next to the walls of Resafa. From a post like this, 65-70 soldiers watched the road between two large cities in the middle of the steppe. Read together with the Sura and Resafa entries, it makes the Roman frontier concrete: large legionary cities, with small towers in between that could see each other.