The haunting "Hell House Altar" is one of the few remnants of an abandoned college that has been a magnet for local legends.

This whimsical castle of grottoes was the labor of love of a French postman, and one of the greatest achievements of outsider architecture.

This abandoned subway station beneath the Waldorf-Astoria hotel is allegedly used to secretly transport presidents.

Deep under Manhattan is the largest construction project in city history. So far, the project has taken the lives of 23 workers, or "a man a mile."

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

A tiny museum housed in a New York freight elevator specializes in the "overlooked, dismissed, or ignored."

A dark, dank room in subterranean Manhattan was the site of a ghastly murder.

The remains of an idyllic small town built for the film 'Big Fish' still stand around a rundown main street.

If New Orleans is the birthplace of the "cocktail," why does their own museum of cocktail memorabilia beg to differ?

A lone cannonball remains lodged in the walls of the Hotel de Sens as a sober reminder of a revolution.

Remains of Roman amphitheater hidden in a sleepy quarter of Paris.

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

An unusual number plate signifies the building's saucy past.

This massive library holds what was once the largest book collection in the world.

A haunting collection of the vanished and disappearing natural world.

Known as the "Dodo Manège," this carousel features a herd of animals that have disappeared—or may be gone soon.

This museum houses an imposing skeleton army comprised of creatures great and small.

A grotto-like lodge decorated with gilded mosaics, rocks and a noisy waterfall was the setting for the most sumptuous pleasure house of 1900s Europe.

The oldest stone house in Paris was built by its most famous alchemist.

This innocuous-seeming building is actually the remnant of a major wartime brothel.

A French museum of wrought iron.

The famous winding walk at Chartres is surrounded in mystery and myth.

A museum of carnival attractions where you are invited to ride the rides.

The macabre collection of Jacques Sirgent, an expert scholar on the undead and all of their trappings.