A floating cat sanctuary on an Amsterdam canal.

The former home of a mad diplomat is said to still be marked in bloody, arcane scrawls.

A collection of biblical memorabilia.

A beautifully eclectic mix of architectural styles.

Museum preserving torture methods from the past.

Cat art as far as the eye can see.

This unattributed sculpture in Amsterdam is hiding in plain sight.

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

Thousands of artifacts relating to human sexuality, including the world's largest sex bike.

An exotic wildlife habitat right off The Strip.

A giant open-air sculpture made of over 200 full-sized boats.

Yo, Adrian!

An ancient ossuary in Rouen.

Medieval museum built over Roman baths that features famous tapestries of a lady and a unicorn.

The celebrated eyesore created by starry-eyed sweethearts.

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

The very center of Paris is surrounded by a bevy of strange good luck rituals.

France's most famous cemetery, with some of its most curious tombs.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

Forgotten and then destroyed by fire, this was once one of the largest saltwater swimming pools in the world.

The giant pair of sexy legs sticking out the window of this costume store have become its main draw.

This private residence was the template for one of the most beloved television homes of all time.

Not merely a museum – but a whirring powerhouse that offers a subterranean peek into the heart and soul of cable car operations.