This Budapest bar allows drinkers to leave their mark on the walls, floor, and even ceiling.

A 19th century artistocrat's mansion, turned into a library, hidden in a modern library.

A sprawling collection of books and manuscripts about ancient Greece that would have put their famed libraries to shame.

What once sat in the world’s spotlight is today a largely disused ghost complex.

This secret coastal village is studded with pastel-colored houses all piled on top of one another.

Where commuters walk through remnants of an ancient Greek necropolis.

Large collection from the 3rd millennium BCE.

The rocky remains of an ancient Greek forest.

This open air archeological site houses almost as much wildlife as it does classical religious artifacts.

An autonomous republic of Orthodox monks.

This statue was given to France by the United States to commemorate the centennial of the French Revolution.

A cave dwelling that was started by the Celts, expanded by monks, and finished by knights.

This former “ante-chamber to the guillotine” has been refurbished to illustrate the brutal history of French justice.

Hundreds of hidden passageways weave through the old quarters of Lyon.

This Parisian fountain is a little bit fantasy and a little bit nightclub.

Down a cobblestone alleyway is a museum dedicated to Romanticism, with a secret garden.

A former top secret nuclear fallout shelter now operates like a hotel stuck in the Cold War.

Massive installation of Europe's negative stereotypes.

Thousands of letters to Santa get delivered to this mailbox in Greenland.

No longer the only, but definitely the oldest, fountain in Greenland.

An experimental forest at the foreground of arboreal science is also the canary in the coal mine for climate change.

1% of Greenland's entire population used to live in this single building, which is now slated for demolition.

The world's northernmost flowers cling tenuously to life on desolate Kaffeklubben Island.

Small Island off the coast of Greenland.