At Monet's beloved home you can still see the Japanese bridge, waterlilies, and weeping willows that were the subjects of some of his most iconic paintings.

This historic island prison holds one of the dungeons from the Count of Monte Cristo even though it is a work of fiction.

A 14th century bridge built as a fortress, where the devil lurks on one of its towers.

A cave dwelling that was started by the Celts, expanded by monks, and finished by knights.

Hundreds of hidden passageways weave through the old quarters of Lyon.

Sacked by Vikings, blessed by William the Conqueror, dealt a fatal blow during the French Revolution—these ruins have seen it all.

Ancient paintings known as the "Sistine Chapel of Cave Art."

The ruins of a Duke's bucolic dream, where camels once roamed alongside "Dutch" windmills and faux-Italian vineyards.

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

This whimsical castle of grottoes was the labor of love of a French postman, and one of the greatest achievements of outsider architecture.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

Remnants of a Victorian garden feature sitting in public woodland.

Wedged between two buildings at the Great Ormond Street Hospital is this secret music installation.

A vast overgrown cemetery, once known as one of London's "Magnificent Seven."

Winding paths and ramshackle mausoleums in the oldest "park cemetery" in London.

Banksy gives themself artistic license with this piece of London street art.

This South London cemetery holds the remains of more than 15,000 people.

This collection of illusory paraphernalia has been culled from the history of London's premier magician's club.

A kaleidoscopic warehouse-maze of handmade neon signs.

This shop and gallery is a modern-day cabinet of curiosities, unassumingly positioned along an urban thoroughfare.

This churchyard arbor is surrounded by hundreds of gravestones placed there by author Thomas Hardy.

A 300-year-old tea shop that brought tea to the English people, not to mention the Queen herself.

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

This grubby wall is said to be one of the Earth's esoteric energy centers.