Famously misunderstood wonder of the ancient world

Human-made caves excavated to hide a secret society of wealthy pagans.

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

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

Paris' fabled purveyor of exotic taxidermy and natural history curios.

The celebrated eyesore created by starry-eyed sweethearts.

A museum on the history of Paris, including a set of Napoleon's toiletries, Proust's room, and relics of the Revolution.

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

A beautifully eclectic mix of architectural styles.

The curios of pharmacist and collector Henry Wellcome.

Cat art as far as the eye can see.

A historic house left in "dramatic still life."

Scattered throughout London are ancient remnants of the city's former bounding wall.

A hands-off space for graffiti artists to hone and display their skills.

The anatomical-pathological collection of a man who changed surgery.

A cluttered and astounding collection of antiquities and curiosities.