Partially collapsed lava tube and cave system complete with concert hall, underground pond, and unique albino crabs.

A motley, fantastical agglomeration of unlikely houseboats along the Shoreham-by-Sea riverbank.

Every year locals tumble 650 feet down to the bottom of the hill chasing a Double Gloucester cheese.

Huge winged monument in the United Kingdom.

The signs of a long buried road can still be found hidden beneath a London sewer grate.

An incarceration museum on the spot of possibly the oldest prison in England.

Like a kitschy mirage in the Mojave, this eatery serves up classic 50s-style diner meals and a dinosaur sculpture garden.

At low tide, you can see the remains of a 17th-century ship just off a Stockholm island.

A simple stone remembers one of the most menacing horses in the Swedish military.

A steel paper plane is all that remains of a crashed aircraft that caused an amazingly small amount of damage.

This historic Amsterdam bar used to accept sailor's monkeys as payment.

This unattributed sculpture in Amsterdam is hiding in plain sight.

This cheese shop also houses a museum devoted to Dutch dairy.

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.

This ancient causeway can flood daily, leaving Mersea Island as a true island for hours at a time, and cutting its 7,000 residents off from the mainland.

Catacombs turned marketplace.

Bangkok's men with dangerous jobs come here in search of protective talismans.

This incredible collection of vintage pinball machines can be played at 25 cents a pop.

A mysterious bridge over a sunken Roman road.

A menagerie of curiously bred creatures.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

Giant statue of a disembodied head.

This surreal art house looks like a geometric version of a small chapel.

Gutted during the Liverpool Blitz, this architectural husk has been left destroyed in honor of the dead.