A modern-day Lascaux cave underneath Paris.

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

A golden plaque marks the site of the mysterious unsolved assassination of the former Swedish prime minister.

This homeless brass fox tugs at your heartstrings from the foot of a Stockholm bridge.

This Stockholm light tower can be controlled by anyone with a smartphone.

The world's largest model of our planetary system.

Venice's island of the dead.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

100 year tradition of fist fights, marked by marble footsteps.

The former Nazi concentration camp stands as a museum to remember this dark chapter in European history.

Poland's oldest salt mine has nearly everything one needs to live underground forever.

An underground city of salt.

This man-made mound monument was built out of soil from all across the Polish empire.

There are thousands of tributes and memorials to the King, but none quite like this one in a Kraków city park.

This Polish cave has housed a dragon, a brothel, and an enduring legend.

Real bones which are said to have belonged to a Polish dragon.

Beneath Kraków Old Town's main square lies a hologram-filled medieval market vampire graveyard wonderland.

20-foot tall lamp mumbles Swedish to celebrate the holidays.

A series of modernist treehouse hotel rooms grace the outskirts of an Arctic forest.

This chimerical bridge/tunnel appears to dead end right into the sea.

Largest island in the Baltic Sea experiences such idyllic weather that roses bloom in the middle of December.

The world's first ice hotel is still one of the most elaborate and beautiful.

Sweden's first nuclear reactor, R1, can be visited 25 meters underground.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.