Four-story concrete hotel never opened to customers.

A trading post in the North Pole where children send letters.

Remains of the artificial harbours invented for the Allied invasion of Normandy can still be seen at sea.

A kitschy, creepy St. Louis mainstay.

Hamburgers are intensely proud of their tunnel beneath the river.

The world's longest and deepest train tunnel.

Lyon, France is home to two remarkably preserved Roman theaters, one dating back to 15 BCE.

The mysterious large white cross visible from the runway is a memorial to a massacre during Spanish Civil War.

French Time Capsule-19th Century home revealed to the public.

The sweet story of how American cargo planes became known as "Candy Bombers" during the Berlin Blockade.

A secret hatch containing two parchments was discovered in this statue over 40 years after its installation.

An homage to the humble watering can.

The NASA scientists behind Apollo 11 started out developing Nazi weapons at this abandoned German rocket factory.

A 30-year-old Sycamore tree grown from a seed taken to the moon and back.

Today this bizarre rooftop phone booth seems like a piece of kitsch but it was once used to spot disastrous storms.

A monument to the small town of master violin makers and its countless luthiers.

The restaurant keeps a hidden séance room on the second floor and reserves a table for the spirit of the former owner each night.

Fantastic views and thousands of love locks.

A natural wonder in south Denmark.

The room where Vincent van Gogh died.

The body of at least one victim of a construction accident was left behind in the collapsed pylon, buried under tons of concrete.

One of the most powerful religious centers in the Middle Ages, dubbed the founder of Western monasticism.

The ruins of an abandoned cemetery are among the last remnants of the old village of La Boulaye before a wealthy landowner had it relocated.

A memorial for a young woman and her ghost, which are claimed to have caused countless deathly shipwrecks.