Cold war icon and onetime "hole" in the iron curtain.

Wedding chapel's mysterious spiral staircase said to be miraculously constructed.

An abandoned facility that has become a place of ritualistic satanic worship, or so rumor has it.

The most unique castle in all of Southern California, entirely constructed from repurposed materials.

Thousands of exquisitely carved stone water storage wells, hundreds of stone steps fill this exquisite medieval stepwell.

Abandoned concert venue legendary for its rock counterculture.

An enormous, inside-out glass globe built in 1935.

An icon among Florida's pre-Disney tourist attractions.

Stalinist skyscraper built with help of cryotechnology.

Gargantuan home of Russian science.

The tallest hotel in Europe.

Small on the outside, big on the inside, this church is an astonishing act of visual deception.

A modernist landscape of water and sci-fi concrete.

Hundreds of hidden passageways weave through the old quarters of Lyon.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.

This Scandinavian island is the site of the first modern observatory.

Not to be confused with the iconic New York City skyscraper, this Chicago building is a vibrant hub for artists.

One of the last functioning antique elevators in Chicago.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

A metal tree emits eerie, melodic notes on top of Lancashire's Crown Point.

The biggest solar telescope in the world helps reveal the secrets of our sun.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

At just six feet two inches deep, it is said by Guiness and Ripley to be the world’s narrowest freestanding office building.

An intriguing three-sided folly is a testament to one man's devotion to Catholicism and the number three.