The world's largest neutrino telescope searches for secrets of the universe at the South Pole.

This massive airship factory is so large that it has its own indoor weather.

The name of this famed hospital was once a byword for the horrors of medical and psychiatric care.

Built by the patron saint of illusionists this Elizabethan manor house is riddled with secret cubbies for hiding priests.

Decades after testing the polio vaccine on unwitting patients, this historic mental hospital sits in ruin.

This unmarked and unloved Manhattan subway grate created one of the most iconic images in American cinema.

A forgotten remnant of the Soviet Union, Transnistria is an unrecognized country hidden behind a heavily militarized border between Moldova and Ukraine.

This massive concrete sculpture is said to be the heaviest communist monument on Earth.

This once-grandiose behemoth of a monument from the socialist era now sits quiet and closed up.

An abandoned saucer-shaped monument in the Bulgarian mountains.

A tree-like building perches on its trunk in the Steglitz neighborhood of Berlin.

Solar observatory doubles as a daring display of Expressionist architecture, much to Einstein's chagrin.

The "Prussian Versailles" that is as glorious today as when it was built.

Terrifying derelict military hospital once housed a recuperating Hitler.

Hundreds of secret cabinets built into the walls of legendary poisoner's private work room.

A hyper-luxurious, 12,000- square foot home might be buried beneath Queens, still waiting to protect you from nuclear missiles.

A strange house built only at night, with rumored mystic inspiration.

A lovers' beach, tucked below the surface of the island, provides a safe haven for romance.

A posh members-only club with a literally dramatic history.

An unassuming secret door once led to a legendary watering hole.

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

An indoor miniature village and labor of love for Laurence Geiringer, a model railroad enthusiast.

The Sun King's military models, saved from the Louvre.

A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.