The Lower Basilica
The Vatican Grottoes occupy the level just below St. Peter's Basilica, consisting of a system of vaults built between 1590 and 1591 to support the floor of the Renaissance building above. Yet their origins trace even further back—to a design variation presented to Pope Leo X by architect Antonio da Sangallo the Younger after Raphael's death in 1520.
Today, the central space of the Grottoes forms a sort of "lower basilica" with three naves, arranged around the papal tombs—the successors of Peter laid to rest near the Apostle they served.
The Clementine Chapel
In 1592, Pope Clement VIII Aldobrandini carried out major expansion works, renovating the medieval crypt and giving it the name "Clementine." Here stands the seventeenth-century altar, located near St. Peter's tomb ("ad caput Sancti Petri")—the closest public approach to the Apostle's burial site.
A Place of Memory
At the beginning of the seventeenth century, as the last vestiges of the old Constantinian basilica were demolished for the new St. Peter's, the Vatican Grottoes became a treasured memorial—a kind of museum before its time—where statues, mosaics, paintings, and inscriptions were preserved as relics of the venerated lost church.
Here visitors can see the last images of the ancient basilica that would never be seen again—internal and external views, alternated with reproductions of individual monuments from the original church.
Modern Chapels & Additions
After the mid-twentieth century, further devotional spaces were added around Peter's tomb: the Irish Chapel (1954), Polish Chapel (1958, expanded 1982), Lithuanian Chapel (1970), Chapel of the Patron Saints of Europe (1981), and Mexican Chapel (1992). A special oratory houses the tomb of Pope Pius XII (1958)—the pope who championed the archaeological explorations that confirmed St. Peter's burial site.
In 1979, a large archway was opened to make visible the front of the Confessio with the Niche of the Pallia—the place closest to Peter's tomb. Chapels dedicated to Our Lady now encircle the Apostle's resting place like a crown.