Holy Grotto of Montserrat Monastery holds one of Europe's mysterious black Madonnas.

Beneath the city of Lourdes, France is a massive, concrete church.

Abandoned Nazi train station turned underground astroparticle laboratory.

In the town of Třeboň, carp is king.

Budapest's Communist-era statues, banished to the suburbs.

Baroque celebration of the end of the Great Plague of Vienna.

Op-art architecture designed for happiness.

A century-old tradition has culminated in a small but singular collection of feline effigies.

Geological storytelling.

Cliffside houses provide a spectacular view from their perch above the valley.

One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

Daily jousts and dancing barrel makers in Munich's mechanical clock.

Rare collection of medieval books under lock and key.

The largest known medieval map of the world.

Pop culture has helped to keep this iconic British building from being destroyed.

One of the few standing Roman lighthouses and a labyrinth of tunnels are a couple of the secrets at this historic castle.

Historic medieval fortified city in southwest France.

A little sculpture with a large wardrobe.

The most visited, and possibly most controversial, museum in Germany.

Swedish skyscraper with a 90° twist.

Giant topiary dog once played a role in a terrorist bomb plot.

Famed architect Antoni Gaudi built this generous thank you gift to a friendly host who housed him during a job.

Despite attempts by local police to discourage it, Beatles-inspired graffiti has been a means for artists to air grievances for decades.

Only spot in the world where an HVDC powerline, a single phase AC and a three phase AC powerline all meet.