Cathedral of Santa Maria Assunta (Il Duomo)

Naples is packed with churches; you can’t walk more than a few hundred meters without spotting one. With over 500 scattered around the city, it's not that surprising. For anyone who loves religious art and ancient architecture, Naples is a real treasure trove. Most churches feel like museums and many are free to visit. But none is more important than the one right here: the Cathedral of Santa Maria Assunta, or Il Duomo. This cathedral has been of great importance to the people of Naples for centuries. Imagine going back in time; forget the shops, the tourists and cars, and picture yourself in ancient Naples. You are standing in the very heart of the ancient Greco-Roman city, on sacred ground that is home to religious temples for thousands of years. The very first Christian basilica was built here in the 4th century by Emperor Constantine, on top of an even older temple dedicated to Apollo. Fast forward to the 13th century, when Charles I of Anjou decided to build a new cathedral on the site of the old basilica of Santa Restituta. Parts of that original church are still inside the current Gothic cathedral, including tombs from the 14th and 15th centuries and a stunning mosaic. Beneath it all lies Europe’s oldest baptistery, built in the 4th century by Saint Severus. Today, the cathedral is the seat of Naples’ archdiocese and is dedicated to the Assumption of the Virgin Mary. But the real treasure inside is the remains of Naples’ patron saint, San Gennaro, or Saint Januarius. The cathedral houses two small vials of his dried blood, dating back to his death in 305 AD. Three times a year, during a lively religious festival –the kind only Italians can truly pull off– the blood miraculously liquefies before a crowd of worshipers. This miracle is said to bring good fortune and protection to the city. If you wish to see the relics, you’ll have to pay to enter the Chapel of the Treasure of St. Januarius; the saint’s body rests in the crypt below.