With the skill of a stage designer, the great Gian Lorenzo Bernini enriched this church's arches with Baroque statues and ornaments, transforming it into an extraordinary organic creation.
After getting a good look at it, begin to explore this beautiful church by starting from the second chapel on the left, the Chigi Chapel. It has the shape of a circular temple, and was made by Raphael at the beginning of the 16th century for the banker Agostino Chigi. Raphael designed the golden mosaics in the dome, while Bernini contributed with the two pyramid-shaped graves and the statues of Habakkuk and Daniel, two prophets of the Bible.
Continue along the left side and go to the back of the church to the Cerasi Chapel, which was designed for the Vatican treasurer by Carlo Maderno, the architect of St. Peter's Basilica. On the altar you can admire the splendid Assumption of the Virgin by Annibale Carracci, while on the sides two masterpieces by Caravaggio await. The first one is called Conversion on the Way to Damascus, where you likely first noticed the large piebald horse standing over the saint who has fallen off, while the realistic figure of the groom emerges from the dim light in the background. The other picture, titled Crucifixion of St. Peter, shows you the moment when the cross the saint is nailed upside down to is hoisted up. Caravaggio focuses on the effort of the three figures trying to lift the cross up, pushing it and pulling it with a rope.
As you can see, the back of the church is shaped like a large shell: it was renovated in the early 1500s by the great architect Bramante. The frescoes on the vault are instead by the Umbrian painter Pinturicchio, while you can see a very rare artistic element in Rome above: stained glass windows. Notice also the the ancient Byzantine icon on the tall altar: it dates back to the beginning of the 13th century and is called the Madonna del Popolo.
I'd also like to point out the first chapel on the right, which belonged to the powerful Della Rovere family: it has fifteenth-century tombs and a fresco by Pinturicchio.
FUN FACT: the scholars wondered how Caravaggio managed to obtain that special contrast between light and shadow.
After several studies, they finally came to understand that he would use two mirrors when painting, one to capture the light, and the other to project the image on the canvas. And he would paint while looking at the second mirror.