Underground

Hidden in a grotto 26 feet below Nottingham's oldest hotel, this stylish subterranean drinking den is notoriously hard to find.

A hidden tunnel leads to a medieval queen's shrine buried beneath a parking lot.

There's a labyrinth of medieval chambers hidden deep below a 15th-century pub.

A galaxy of glowworms—larvae of a gnat—hides deep in the belly of these caves.

The world’s largest underground marble quarry is hiding in Vermont.

The burial place of an obscure North African saint was turned into a macabre body preservation factory for the 17th-century Neapolitan elite.

The world's first hotel built in an abandoned water-filled quarry.

Colorful lights and mirror-like brine pools create trippy illusions within the historic mine.

The secret room where early Bolsheviks cranked out propaganda fliers on a smuggled printing press.

An ancient underground cultic temple where sunlight penetrates on the summer solstice.

Italy's third-largest Roman arena gives a peek into the underground operations beneath the ancient spectacles.

The hellish conditions of this abandoned mine that snakes beneath the Pacific Ocean gave it its diabolic name.

The gorgeous entrances into the city's underbelly look more like grand halls than subway stops.

This huge abandoned fortress hidden inside a mountain holds a world of subterranean secrets.

It's hard to believe the dizzying patterns covering this abandoned mine are completely natural.

A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.