Hidden beneath the rugged Apennine mountains in Italy’s Marche region lies one of Europe’s most spectacular natural wonders: the Grotte di Frasassi. Italy’s largest and most majestic limestone caves—discovered in 1971—stretch for over 11 miles beneath the surface, offering a surreal, almost otherworldly experience.

The crown jewel of the cave system is the Ancona Abyss, Europe’s largest single cavern; in fact, it’s so vast that it could easily accommodate Milan’s Duomo inside it. The chamber stuns with its sheer scale. As you continue to explore the other chambers, you’ll marvel at the towering stalagmites and detailed stalactites formed by nature over millions of years.