All the appears to be painting in St. Peter's, is in fact mosaic work, from the mosaic studio in the Vatican, which is the only place in the world where a painting can be reproduced in mosaic with perfect exactness. They use mainly composition stone.
Continuing along the right aisle and immediately on the right is the Chapel of the Crucifix, containing a XII century crucifix, ascribed to Cavallini. Opposite the chapel of the Crucifix is the memorial to Christina of Sweden by C. Fontana, one of the few women buried in St. Peter's. She abdicated and converted to Catholicism, which her father, Gustavus Adolphus, had fought against during the Thirty Years War and she came to Rome in 1655. Her grave is in the crypt underneath the church. In the next chapel is the mosaic reproduction of the Martyrdom of Sebastian by Domenichino, XVII century. In a open glass casket underneath the altar lies the body of Blessed (Beatus) Innocent XI, XVII century, his face and his hands are covered with silver.
On the left of it is the fine bronze statue of Pope Pius XII by Messina, 1964. In the same aisle is the splendid Chapel of the Blessed Sacrament; above the altar is the glided bronze pyx by Bernini, inspired by the Tempietto di Bramante in the Church of St. Peter's in Montorio. Behind the altar is the only oil-painting of the whole Church: the Trinity, by Pietru da Cortona. Beyond the chapel, on the right, is the monument to Pope Gregory XIII, by Rusconi, XVII century, the pope who reformed the old Roman Julian Calendar. There is a relief recaling this event which took place is 1582.
We return to the central nave and we find ourselves in the part of the Basilica built by Michelangelo. He planned the church in the form of a Greek Cross, the embodiment of the symbol of the Cross, while the imens dome suggests the idea of the sky being inseparable from the Cross. Almost fifty years after he had carved the Pieta for the old St. Peter's, Michelangelo, most reluctantly, took in hand his greatest architectural work, which was to be the culmination of his extraordinary life. However, he didn't live to see his dome completed; at the time of his death he had raised it to the height of the drum. Although Della Porta and Maderna altered Michelangelo's original plan, we can still say that this is his greatest work as an architect.
