Dating back almost 400 years, the oldest public collection library in the United Kingdom was once the study hall of Karl Marx.

Perfectly preserved ancient monastery in an impossibly dramatic location on a rocky island in the Atlantic.

The largest greenhouse in the world is home to over one million types of plants.

Mysteriously stacked storefront paths give this medieval British town an iconic style like none other.

The gloomy ruins that inspired Bram Stoker to bring Dracula to life.

A Victorian Gothic masterpiece housing a world-class collection of rare books and manuscripts.

A small town Romanian cemetery filled with darkly humorous gravestones.

The final resting place of the great escape artist, where some still gather to wait for his escape from death.

A haunting exhibit in a wildlife refuge center highlights threatened species and the conservation efforts needed to save them.

A nearly 500-year-old sculpture depicts a man eating a sack of babies, and no one is sure why.

The largest portal tomb in Europe has a capstone weighing around 150 tons.

An Art Nouveau building covered in animal gargoyles and grotesques.

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

This unattributed sculpture in Amsterdam is hiding in plain sight.

This bug-eyed water wheel uses the power of the Sun to clean up Baltimore Harbor.

This unassuming museum's slogan translates to “there is a limit of sadness, anxiety has no limits."

A reconstructed medieval gateway that was the magnificent entrance to the capital city dating back to 1037.

The medieval prince founded the first library in Ukraine at Saint Sophia's Cathedral where he was interred.

These lesser-known Maltese catacombs date back over 1,700 years.

The site where Poe "in great distress, and ... in need of immediate assistance" likely died.

The attic of a four-century-old canal house hides a clandestine church.

A meditative space out of a fantasy story.

Hidden dwellings in the cliffsides of North Togo used by local Moba tribes to evade 18th-century slave traders.

A remarkable lava formation encloses a line of Buddhist statues that can't be accurately counted, according to local mythology.