Naples Cathedral (Duomo di San Gennaro)

Three times a year, the entire city of Naples holds its breath and stares at a vial of dried blood. If the blood of San Gennaro liquefies — as it has done, with a few terrifying exceptions, since at least 1389 — Naples will be safe. If it doesn't, disaster is coming. The blood failed to liquefy before the 1980 earthquake that killed nearly 3,000 people in southern Italy, and again in September 2020 at the start of the COVID-19 pandemic. Neapolitans do not treat this as folklore. They treat it as news.

The cathedral itself was begun in the late 13th century under Charles I of Anjou and consecrated around 1315, though it incorporates much older structures — step inside the Basilica of Santa Restituta, accessible through the left nave, and you're in a 4th-century church built on top of a Greek temple to Apollo. Dig further and there's a Roman building underneath that. Naples is a layer cake of civilizations, and the Duomo is where you can see the strata most clearly.

The Chapel of the Treasury of San Gennaro, added in the 17th century, is so lavish it practically constitutes its own church. The silver bust reliquary containing the saint's skull is encrusted with jewels, and the treasury's art collection includes works by Domenichino and Jusepe de Ribera. The chapel was built after a plague in 1527 killed an estimated 60,000 Neapolitans, and the city vowed to build the most magnificent shrine it could if San Gennaro would intercede.

Rick Steves puts Via Duomo on his Naples walking route, and the cathedral is the reason. Come for the architecture, but come on a miracle day — the first Saturday of May, September 19th, or December 16th — and you'll witness something no other city on earth can offer.