A French valley with forests so lush it was nicknamed "the Small Amazonia of the Pyrenees."

A subterranean shelter remains intact under a busy Paris railway station.

A distillery built on (and above!) mobster Dutch Schultz's Prohibition-era underground moonshine business.

Walk a trail through a historic Quaker town that outlawed slavery in 1777 and was a major waypoint on the Underground Railroad.

The Cambridge pub where Francis Crick announced that he and James Watson had discovered the DNA double-helix.

The abandoned grounds and derelict greenhouses of this once-magnificent Edwardian estate are now a nature preserve open for exploration.

This network of tunnels housed an entire village for years, and even had a hall for screening movies.

Small teepee-like houses built for TB patients have become sheds, studios, and bus stops around Colorado Springs.

At the center of an island in the middle of the Indian Ocean is a deep chasm ringed by tall waterfalls.

The remains of the worst maritime disaster in the history of the "Graveyard of the Pacific."

From under the bed of one of the co-founders, this server helped launch the notorious file-sharing website.

What might look like a cliffside sacrificial altar at first glance is actually a stone compass pointing to cities and lighthouses all around the world.

The name of this tiny pocket park tucked between two buildings on Manhattan's Upper West Side is Latin for its location: "seventy-one."

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.

This Cold War–era underground city includes offices for Mao Zedong and Lin Biao.

An astounding annual light display honors the victims of one of Japan's most devastating earthquakes.

The collection of 80+ pieces created between the years 1100 and 1500 is intended to be seen, heard, smelled, touched, and tasted.

A festival where people vie to be bombarded by exploding clusters of fireworks.

A restaurant on Staten Island showcases a different grandmother’s cooking every night.

A hermit's tiny cell built into the cliffside that saved him in South Pembrokeshire.

A plaque commemorates the spot in the Oregon woods where the first-ever Geocache was hidden.

The hollow trunk of this 650-year-old tree was used as a hideout by two Jewish brothers during World War II.

The first mosque in Ghana is known as the "Mecca of West Africa."

This pump on the bad side of Victorian London betrayed a horrifying revelation about the water supply.