The sinister ruins of one of the worst dam failures of the 20th century lie in this astonishing alpine setting.

A spectacular rainbow of stained glass makes the "Pink Mosque" one of the most beautiful in Iran.

There's a labyrinth of medieval chambers hidden deep below a 15th-century pub.

The world's first purpose-built motor racetrack was destroyed by the outbreak of two world wars.

This 170-year-old Swiss guesthouse built into the side of a mountain is best accessed by a cable car.

This oddly placed 15th-century church is one of only six bridge chapels left in England.

At high tide this strange footbridge appears to have no purpose whatsoever.

A breathtaking flower tunnel bursts with beautiful golden blossoms.

A beautiful lighthouse with as many steps as days in the year, as many windows as weeks, and as many levels as months.

Abandoned boats decaying in the largest ship graveyard in mainland Britain.

A giant repository of accidentally discovered cave paintings up to 30,000 years old.

Breathtaking Byzantine paintings cover the inside of this 12th-century church.

A mysterious, hidden cluster of Buddha sculptures carved into the rocks.

This once-booming gold mining hub was basically abandoned overnight.

The wooden airship was the largest flying boat ever built.

A harrowing trail up a mile-high mountain.

A sacred mountaintop temple offers a fine cup of tea to visitors who can survive the journey.

This antique prison is a tourist attraction with a sordid past.

Wedged between two buildings at the Great Ormond Street Hospital is this secret music installation.

An small and easily overlooked archaeology museum chock full of Egyptian artifacts.

An unusual round church in London with a Templar past.

A cluttered and astounding collection of antiquities and curiosities.

On October 17, 1814, a 15-ft. wave of beer ran rampant through the streets of London.

Hidden beneath the streets of London is a secret subway that only carried mail.