Pompeii was lost to us for many centuries until it was rediscovered again, initially in 1599, and properly in the 1700s. It is one of the world's greatest archaeological sites. The volcanic eruption wiped out the population of Pompeii, but the town they lived in was remarkably well-preserved because of the combination of ash and lack of moisture that sealed the town, and essentially turned it into a time capsule.
The Renaissance-era St Peter's Basilica is one of the largest churches in the world (and the home-church of the Pope). Highlights include the dome (the biggest in the world), Bernini's Baldacchino (the centerpiece of the church), and Michelangelo's Pietà (the only artwork he ever signed).
For both the pious and the casual visitor, a trip to St. Peter's is an awe-inspiring trip into the heart of Vatican City.
The Pontifical Basilica di San Nicola is an important church in Bari, located in southern Italy. Its crypt is said to shelter the relics and bones of Saint Nicholas, of Santa Claus fame.
Visitors can explore the basilica's magnificent interior alone or with a guide, and learn how it was built between the 11th and 12th century. It is now an important pilgrimage destination for Roman Catholics and Orthodox Christians from Eastern Europe.