An underground city of ancient quarry tunnels hid thousands of Allied soldiers in WWI.

A monument to the thousands of Canadian soldiers who died capturing the French ridge during World War I.

One of the last doorless, continuously moving elevators still in use in the U.K.

The world’s first museum dedicated to the history of childhood opened in Edinburgh in 1955.

The final resting place of soldiers' loyal canine companions.

This downtown Dallas art installation is always on the lookout.

Continuing the tradition of the dime museum in style.

A unique collection of diving equipment spanning antiquity to the present day.

A monument celebrating the idea of reaching inaccessible places.

The former home of the Nobel Prize-winning American writer is now home to dozens of six-toed cats.

According to the Guanches, the aboriginal people of the Canary Islands, the king of evil lives inside this volcano.

This historic toy museum brings a little whimsy to a city not usually remembered for such things.

A castle from the Holy Roman Empire that hosts traveling youth... in its stables.

The world's most active stratovolcano is almost always erupting.

This one-time health resort was used by aristocrats around the world.

A whimsical bridge adorned with decorative dragons.

Strange rumors surround the artist who created these solemn metal guard dogs.

A miniature train-ride through Slovenia's largest cave system.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

One of the best-preserved Roman amphitheaters is still used today, but for less brutal events.

Northern Ireland's Brobdingnagian stepping stones.

These barriers stand as stark reminders of Northern Ireland's troubled past.

A giant sculpture of the legendary "Salmon of Knowledge" celebrates the return of fish to Belfast's River Lagan.

A museum marks and documents the site of the Titanic's launch.