[1] The sanctuary is made up of a nave with three spans, without collateral or chapels, a transept and three apses.

The central apse, preceded by a cradle vaulted, was built at the end of the 11th century.

The two small lateral apses are of unequal depth, and are roughly constructed in two-meter-thick walls, showing an origin largely anterior to the 11th century.

There are also two lateral towers of a Gallo-Roman gate, or of elements of a Frankish or Visigothic fortress.

The walls are covered with an exceptional set of Romanesque frescoes dating from the 11th century; Externally, the three apses are not ornamented: the apse presents three flat faces executed in particular with stones of great Roman apparatus and antique marbles recovered from the Gallo-Roman walls of the city.