A floating cat sanctuary on an Amsterdam canal.

Established in 1638 to battle the Black Death, Hortus Botanicus Amsterdam is a treasure trove of rare flora.

An Amsterdam street lined with antique shops each one dedicated to a different obscure collection.

A French artist's vague warning hangs over Belleville.

A series of abstract, silly sculptures represent the works of a great modern classical composer.

This banal Parisian entranceway is not what it seems.

Dedicated to the history and culture of smoking, this small museum now includes a vape lounge.

In this Parisian garden's grotesque former life as a zoo it fed exotic animals to the bourgeois and put humans on exhibit.

This museum in a Paris apartment gives a unique look at the iconic French singer's life.

A curious collection of locks and keys.

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

The subterranean "lake" below the Paris opera house inspired the Phantom of the Opera's lair.

This surreal statue brings a famous French novel about a supernatural cad to arresting life.

A subterranean shelter remains intact under a busy Paris railway station.

In the best of all possible worlds, everyone will get a chance to see this statue in which Voltaire's heart is interred.

Natural history museum celebrating biodiversity with a parade of taxidermy animals.

The largest medical and anatomical collection in France lies hidden from the public.

A majestic lion statue guards this Parisian botanical garden, and feeds on an unsettling item.

A grotto-like lodge decorated with gilded mosaics, rocks and a noisy waterfall was the setting for the most sumptuous pleasure house of 1900s Europe.

A surrealist timepiece by the artist of melting clocks.

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

France's national museum of scientific and industrial instruments.

A mechanized clock where a man fights off a dragon, crab, and rooster.

Walk upon the mementos of the dead in this Parisian courtyard paved with medieval tombstones.