The interior of the Madeleine will astonish you. It's like taking a trip back in time. While the church has a rigorous, square Neoclassical style on the outside, its interior reveals its late-Baroque origins. Passing through the impressive bronze doors created in the mid-1800s which depict the Scenes of the Ten Commandments, you enter a large, spacious room covered by three domes in succession and lined with stuccoes, sculptures, paintings, and mosaics. Its dimensions are remarkably impressive: the church is over 100 meters long, 43 wide, and 30 tall.
Madeleine's interior was decorated during the Restoration period, after 1815, in a climate of rediscovered religious fervor. Here you can admire the largest religious construction site of the early 1800s, which involved the best French artists of the time.
Of the many significant works of art, you should definitely see the vast fresco by Jules Ziegler titled The History of Christianity that's located at the back of the church in the semi-circular crown. It depicts Jesus among the apostles as well as various historical figures, including even Napoleon Bonaparte in the middle, dressed in his imperial garb and accompanied by his symbolic eagle.
In front of a large group of grooved columns arranged in a semicircle, up on the high altar you can admire a large marble group depicting the saint the church is dedicated to, Mary Magdalene, while she is being carried up to heaven by some robust and equally graceful angels.
Even more important in the history of nineteenth-century sacred sculptures is François Rude's marble group depicting the Baptism of Christ, located in the church's vestibule.
FUN FACT: before leaving the church, you should definitely admire the immense organ in the entrance wall. As I mentioned, Camille Saint-Saëns, one of the greatest French composers of the second half of the 1800s, played those keys for twenty years. His concerts were considered a surprise event because the organist had the habit of improvising without ever following a predetermined schedule.