Once Langdon and Vittoria decipher the clue and realize they are in the wrong place, they race to the Piazza del Popolo. Here they find the Obelisk of Ramses II (topped with stars and a mountain, the symbols of Pope Sixtus V who had it placed there in 1589).
Of course, they also find the church of Santa Maria del Popolo and head to the Chigi Chapel.
Although the Pantheon is where Raphael is buried, the clue referred to a tomb he had created for wealthy banker (and notorious playboy) Agostino Chigi. Chigi commissioned Raphael "to convert earthly things into heavenly" in the decoration of his tomb.
Chigi died in 1520, and so did Raphael. The work was completed and added to by Bernini in 1652.
Like with the Pantheon, you do not need to be a fan of Angels & Demons to visit Santa Maria del Popolo. The church contains one of the richest troves of Renaissance art in Rome. In addition to works by Raphael and Bernini, you'll find exquisite frescoes by Pinturicchio (who painted my favorites in the Piccolomini Library in the Siena Duomo). And, there are two Caravaggio masterpieces.
You can see a whole series of images of the gorgeous church interior here.
Santa Maria del Popolo is well worth a visit when you are in Rome. It's a functioning church, free and open to the public. Usual dress code enforced (no shorts or sleeveless tops), and quiet respect is requested.
I'll leave you with a story of its earliest days.
In the Middle Ages a legend arose that Nero's ashes were buried beneath a walnut tree growing on the site where the church now stands. Local people believed the area was haunted by the evil emperor's ghost. It was said that the large ravens roosting in the walnut tree were demons tormenting Nero for his crimes. When the first church was built here in 1099 by Pope Paschal II, he ordered the tree cut down, and blessed the site to end the hauntings and supernatural events that had terrified people for so long.
Next time, we'll follow the Angels & Demons heroes to Santa Maria Vittoria.