Thanks to a recent deep cleaning to remove layers and layers of grime, the church's interior almost vibrates with color. Look around, and you'll see spectacular 19th-century murals, elaborately decorated columns, and overhead, a deep-blue vaulted ceiling covered with 3,000 golden stars.

By 1824, the restoring group had assembled marble columns and stained glass windows from other Paris buildings destroyed during the Revolution buildings, which had been fortunately preserved in the Museum of French Monuments. In 1843, the artist Hippolyte Flandrin began the largest project of all, the redecoration of the nave. This was not a restoration, but a re-imagination of a medieval church. For this purpose he employed colourful frescoes illustrating scenes of the Old Testament which announced the coming life of Christ. His work was carried out between 1856 and 1861.