The true depths of these stunning Moroccan caves are unknown.

Exploring the wilder, more passionate sibling of Erg Chebbi feels like discovering a secret sun-kissed planet from another galaxy.

One of the most spectacular canyons in the world.

A medieval, mosaic-lined baptistry built by a heretical Christian sect.

A domed disco abandoned since the '70s now attracts artists and explorers under its unique roof.

This giant middle finger statue sends an unambiguous message to Italy's bankers.

Nestled in the heart of Milan is a real wunderkammer of morbid curiosities.

Invented in the mid-19th century, this machine could send copied images via telegraph lines.

This curious building hides eclectic details like medieval gargoyles alongside naked angels and Art Nouveau mosaics.

This small Milan street is filled with colorful homes and a rich history.

Long-abandoned art nouveau baths beneath Milan's Piazza Oberdan.

Two very green residential towers cleaning the air in one of Europe's most polluted cities.

An ancient artistic garden parlor full of hidden water wonders.

This clifftop arch is a natural stunner.

The glowing blue Nymphaeum of Emperor Tiberius.

Amalfi's pre-industrial history is slowly being engulfed by the lush vegetation of the Ferriere Valley.

This medieval Italian town is a sheer (and beautiful) cliffside defense.

During World War II, the Shroud of Turin was secreted to this remote southern Italian complex.

Geometry and mystery come together in an epic show of octagonal masonry.

The sunlight passing through the opening of this huge cave system creates a magical effect.

Dramatic sea stacks adorn the coast of this small village on the Adriatic coast.

One man's quest to fix his toilet unearthed over 5,000 artifacts spanning more than 2,000 years of history.

Ride a boat through this magnificent underground world, which now doubles as a theater.

The steel cable lets adventurers zoom between two mountain towns at speeds of up to 75 miles per hour.