This is regarded as the oldest original church still in existence in Austria. It was first documented in 799.
A rectangular building that is no longer visible, partially extending into the nave, probably dates from the Agilofingian period (before 788). During the Carolingian period (after 788), the central structure was erected using debris from Roman buildings. This can be seen on both the inside and outside, while the ground plan is marked by stone slabs.
The building was redesigned as a bay church in the 11th century and the pillar arches were filled in. There are Romanesque and Gothic door and window arches dating from later alterations. Inside the building, Roman stone inscriptions and a furnace can be seen. The first bay contains a copy of the Volto-Santo picture by Lucca (around 1440).
The interior of the church can be viewed through a glass door. Entrance into the church is only permitted with a tourist guide.