The ruins of an Estonian prison are drowning in the quarry lake where the convicts were once forced to work.

This 700-year-old street food market features baby octopus and soy donuts.

Tokyo’s only Vaudeville-cuckoo clock–steampunk-Victorian curio cabinet time piece.

This faux-seedy Japanese arcade is made up to look like a maze of alleys straight out of a cyberpunk dystopia.

The original "capsule building" is a masterpiece of Metabolist architecture.

The most powerful waterfall in all of Europe.

A sulfuric martian landscape that looks far better than it smells.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

This bronze boar's snout has been rubbed to a golden sheen by visitors seeking good fortune.

A large grotto built in the 16th century amidst Florence's famous Boboli gardens.

Cave shrine on Monte Pellegrino.

Italian cave with exceptional acoustics and an unsavory history.

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

A hands-off space for graffiti artists to hone and display their skills.

London's last remaining public soapbox site has seen speeches from Karl Marx, Vladmir Lenin, and George Orwell.

The remains of Crystal Palace Great Exhibition of 1851.

Thanks to modern navigational tools we now know that the true prime meridian runs through a park next door.

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

Gardens representing parts of Asia, Europe, and the Mid East are tucked away among the Soviet-style buildings in East Berlin.

Floating swimming pool within a moored vessel.

Art and a pun, all in one.

This water-tower-turned-high-end-apartment building was once the site of an early Nazi concentration camp.

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

The one-time stronghold of the noble Douglas family, now home to ghost sightings and nesting birds.