The burgus in St. Johann im Mauerthale

From the middle of the fourth century AD, the Roman Empire was in crisis once again. It was shaken by civil wars and invading tribes – the Iazyges in the east and the Quadi in the north. The last major expansion of the Danube Limes took place under Emperor Valentinian (364 to 375 AD). Not only were small or residual forts erected in the corners of what were once large military camps, but bases known as burgi were also built or expanded.

A burgus on the Danube

A Roman burgus of this kind was also found in St. Johann im Mauerthale by means of archaeological investigations and in-depth architectural analysis. The watchtower was to the south of today’s church and protected the end of a promontory on the south bank of the Danube. It had an almost square ground plan with a length of around 12.40 m; the wall thickness on the ground floor was 1.60 m. With a height of over 8 m, the watchtower had at least a ground floor and an upper floor. The ground floor was fairly dark due to its small slit window, but this meant it was well protected. There is evidence of two arched windows on the north side of the upper floor. The burgi of Bacharnsdorf and Rossatzbach (at the end of Windstallgraben) have almost identical dimensions in their expansion phase in Late Antiquity.

Basic substance of the church

Large parts of the Roman building structure have been preserved in the present-day church of St. Johann, with the entire south wall of the nave – which was built in the Romanesque period (11th century) – and the north and east walls of the Gothic tower (14th century) dating back to Late Antiquity. The fact that the church was built onto the north facade of the burgus in the High Middle Ages would also explain the unusual orientation of the nave towards the north – and not towards the east, as is customary.