A dilapidated dock tells the story of Titanic's missed arrival.

A tiny islet just off Long Island offers a wealth of infectious curiosities.

Elevated freight railway turned wildly successful urban park.

This beautiful building in the heart of Manhattan's Financial District was empty for decades.

A historic 1890s architectural masterpiece with an iconic clock tower that, once open to the public, now faces an uncertain future.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

World's first "penitentiary," meant to be humane, drove men insane.

19th century tunnels burrowed under Liverpool.

The internet as provided by a James Bond villain.

A tunnel of hardened lava along Maui’s famous Road to Hana.

A nightmare for the claustrophobic lies hidden in Southeast Asia.

In the middle of downtown Brooklyn lies a 165 year old secret hidden right below the surface (closed to the public indefinitely).

The vast, legendary catacombs hold secrets much stranger than stacked bones.

Poland's oldest salt mine has nearly everything one needs to live underground forever.

The curious underground history of keeping Paris clean.

An underground city of salt.

A neutrino detector built into the largest man-made underground cavity in the world.

The world's largest drain sits below the city of Kasukabe, Japan.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

Huge concrete structures designed as an early warning system for Britain to detect enemy aircraft.

Enormous underground chamber built to detect 'ghost particles' of the universe.

The only Bahá'í house of worship in North America and one of only a handful worldwide.

A science teacher's dream.