Tucked away in a downtown Stockholm park are the remains of a World War II defense position.

The single richest source of elemental discoveries in the world.

The discovery of an old wall led to the creation of this fascinating museum about the city in the Middle Ages.

Street artists transformed this abandoned industrial neighborhood into one of Europe's largest graffiti exhibitions.

An ancient Viking runestone hidden in plain view in Stockholm's old town.

Now a hotel, this former bank was the site of a robbery that spawned a psychological phenomenon.

Dine on food tied to Viking history and legend at this subterranean Stockholm spot.

This Greek temple, open only an hour a day, was the site of a war of tastes between an architect and an artist.

This museum promotes informed contraception by documenting its often secret past.

Macabre museum devoted to historical Viennese murders.

Once a path for Jewish funeral processions, this unassuming alleyway is rich in local lore.

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

A unique Holocaust memorial tells the personal stories of the Jewish residents exiled from greater Berlin.

A fascinating insight into daily life in the Eastern Bloc.

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

A narrow passage next to a cafe leads to a courtyard exploding with murals, tags, and paste-ups.

A slice of central Asia in the middle of Berlin.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

An industrial site turned into Hungary's most cherished natural wonder.

Some of the greatest minds in the history of Hungarian art and science converged in this café.

A Trabant car, a kangaroo statue, and a plethora of plants take over this abandoned-factory-turned-bar.

This off-beat, quirky communism-themed bar isn't afraid to poke fun at its history.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

This village in Bohemian Switzerland hosts more than 300 wood carvings inspired by fairytales, folklore, and other oddities, as well as a series of Communist-era tanks