In the 12th century the eastern part was vaulted, and the east apse was completely rebuilt in a Late Romanesque style.

In the southeast corner of the ancient Roman town was a large temple precinct dedicated to the Capitoline Triad. About 690 Plectrudis, the wife of Pipin of Heristal, founded a convent there, its church making use of the massive foundations of the destroyed temple. After repairs or alterations in the 10th century, a large-scale rebuilding began in the first half of the 11th century (first altar consecration 1049, final consecration 1065). The church was built in a style found at that time only at Speyer Cathedral. In the 12th century the eastern part was vaulted, and the east apse was completely rebuilt in a Late Romanesque style. Around 1240 the nave was given Early Gothic rib vaults.