Rome's churches are filled with countless religious relics. In the Middle Ages, relic veneration became obligatory and every church in Christendom was required to have a holy relic. Relics can include anything from the body parts of a saint to shards of the True Cross to pieces of cloth that have rubbed against a saint's tomb.
Rome has some of the most important and unusual relics, as you can read in the book "An Irreverent Curiosity: In Search of the Church's Strangest Relic in Italy's Oddest Town". Inspired by the book, the following list includes some of the sacred relics you can see in Rome and the Vatican City.
Saint Peter's Basilica
The "Mother Church" was built upon the tomb of Saint Peter, the church's first Pope. Saint Peter's Tomb is located directly below the altar. His tomb, as well as the tombs of dozens of others popes including John Paul II, are located in the crypt. A few other papal reliquaries, including John XXIII, are on display in the church itself.
San Giovanni in Laterano, the church of the Bishop of Rome (i.e., the Pope), was the primary basilica of the Catholic Church before Saint Peter's Basilica was erected. Together, San Giovanni and the adjacent Sancta Sanctorum, the "Holy of Holies," contain some of the holiest relics in Rome. Reliquaries include the heads of Saints Peter and Paul; the Holy Stairs (Scala Santa), taken from the palace of Pontius Pilate; and wood from the table used during the Last Supper.
Santa Maria Maggiore, nearby on the Esquiline Hill, holds several precious relics. It has the relic of the Holy Crib, shards from the Holy Manger, a piece of the True Cross, and the tombs of St. Matthew, St. Jerome, and Pope Pius V.
The primary relics of Basilica San Paolo Fuori Le Mura are the tomb of Saint Paul and a set of chains said to be the prison chains of Saint Paul. Relics from other saints and popes can be seen in reliquaries housed in the church's Chapel of Relics.
Santa Croce in Gerusalemme
This large church not far from San Giovanni in Laterano and Santa Maria Maggiore houses a number of (sometimes disputed) relics from the Passion of Christ. These include the Titulus Crucis, the inscribed sign which hung over Christ during his crucifixion; two thorns from Jesus's crown of thorns; and three pieces of the True Cross. Here you'll also find the doubting finger of St. Thomas.
Santa Maria in Cosmedin
This church, which also houses the Bocca della Verita, a great photo op in Rome, contains the reliquary of Saint Valentine that includes the saint's skull.
The "in capite" in this church's name stands for "head," which in this case means the head of John the Baptist. A fragment of the saint's head is kept here.
Santa Maria Sopra Minerva
St. Catherine, the Patron Saint of Europe, is buried beneath the altar in Santa Maria Sopra Minerva. Three former popes are also buried here – Leo X, Clement VII, and Paul IV.
San Pietro in Vincoli
This small church near the Colosseum is also known as Saint Peter in Chains because it houses the prison chains of the church's first pope.
Santa Maria in Aracoeli
The remains of St. Helena, Constantine's mother who brought back so many of the Passion relics from the Holy Land, are kept in this hilltop church near the Capitoline Museums. Pope Honorius IV and Saint Juniper are also buried here.