Castra of Zwentendorf, Roman military fortification in Zwentendorf an der Donau, Austria

The Castra of Zwentendorf is a Roman auxiliary fort of the Noric Limes, about 1.5 km west of Zwentendorf's centre between the L112 road and the Wagram, on a low terrace above the Danube. Nothing stands above ground: the excavated south-western part was backfilled after digs in the late 1950s and early 1960s, and the river has washed away the northern half. A step in the terrain still marks the terrace edge.

The fort was built in the early imperial period and served as part of Rome's defensive line along the Danube for several centuries. It played a key role in protecting the empire's northern frontier from external threats.

The fort's garrison was the cohors I Asturum, known from brick stamps found on the site and from military diplomas for Noricum; a lead tag (tessera) found at Zwentendorf names a standard-bearer (signifer) from Asturis. Because of these finds, researchers such as Herma Stiglitz linked the site with the name Asturis, while the Tabula Peutingeriana station Piro torto is not mentioned in the Notitia dignitatum. The fort was built for about 500 men, a cohors quinquenaria.

Nothing of the fort is visible above ground: the excavated remains were backfilled after the digs of the late 1950s and early 1960s because the land is farmed. The area, an arable field and the edge of a small wood called "Remise" or "Weingartl", lies about 1.5 km west of Zwentendorf's centre, off the road to the Zwentendorf nuclear plant, between the L112 and the Wagram. A step in the terrain still marks the Roman terrace.

Nothing of the fort is visible above ground: after excavations in the late 1950s and early 1960s the remains were backfilled because the area is farmland. What survives is a step in the terrain, about two metres high, marking the terrace above the old Danube bank. The river has since washed away the northern half of the fort.