A journey into the heart of the first church of Western Christianity, a treasure trove of one of the most varied and expressive artistic heritage in the world. A photographic campaign specially created to bring the reader closer to the masterpieces of the Basilica, symbol of Christianity. St. Peter's Basilica as we know it today is characterized by a symbolic system that refers to the origins of Christianity and the precepts of the Catholic Reformation. This symbolism has its apex in the relationship between the central dome, the altar and the tomb of the Saint, which connected to each other raise the vertical axis of encounter between the earth and the supernatural, and cross the horizontal axis centered on the square in front of the basilica. But it is above all in the mosaics that the message unfolds extensively: we find mosaics in the central dome, in the side chapels, in the domes of the individual chapels and in the altarpieces, creating the largest mosaic apparatus in the world. Each chapel, with its dome and altarpiece, harmonizes with the others and intertwines its own dialogue with the history of the Church and her doctrine. Leading the reader through the harmony and grandeur of these mosaics is the intent of this volume, which represents an essential iconographic reading, edited by the Veneranda Fabbrica di San Pietro, to understand the space and images of the Vatican basilica, still today an extraordinary expression of human creativity, artistic genius and Christian faith.