A beautiful but toxic fountain of mercury.

The tomb of history's greatest potato promoter is surrounded by tubers.

Former hunting lodge of a duke who was an avid collector of impressionist works.

Hidden away in a modern library are the remains of one of the 18th century's most celebrated wunderkammers.

Exquisite wall sculptures carved in secret by an early quarryman in an obscure corner of the Paris Catacombs.

A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.

This massive library holds what was once the largest book collection in the world.

Amsterdam's narrowest house facade is a monument to 17th-century tax evasion.

This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

Cat art as far as the eye can see.

An abandoned swimming pool decays on the outskirts of Berlin.

This little museum is making sure that the art and history of the graffiti sticker is not scraped from history.

Where once there was a train station bathroom, there is now this German burger joint.

A whimsical and twisted animatronic monster tour beneath the streets of Berlin.

A preserved portion of an ancient Athens barrier is displayed in a hotel basement.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

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

After 11 years of reconstruction work, Slovakia's finest hilltop chapel complex is finally reopen to the public.

The blood-soaked ruins of the castle where the murderous Blood Countess was walled in alive.

These historic defenses ensured the city within would survive hundreds of years of occupations, sieges, and invasions.

Mausoleum and Holy Seat of Antiochus I of Commagene.

Turkish adventurer antiques in the heart of the Grand Bazaar.

Once described as the "Eagle's Nest," this ruined ancient city rests on a remote mountaintop.

A feminist who put a pretty face on suffrage when she rode a horse through the Capitol.