The Church of Saints Nazarius and Celsus obtained the status of historical monument in 1840. Around this time, the architect Eugène Viollet-le-Duc renovated the church along with the rest of the citadel. In 1898, the church was elevated to a minor basilica. The sandstone basilica's floor plan is based on a Latin cross, internally measuring 59 m in total length, 16 m in nave width, and 36 m along the transept.