The history and future of cannabis.

The celebrated eyesore created by starry-eyed sweethearts.

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

This hidden Art Nouveau courtyard is an opulent feast for the eyes.

Architectural monsters are devouring this palace's every door and window.

The skull of the patron saint of lovers lies in the Basilica di Santa Maria in Cosmedin—maybe.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

Sitting on an Italian hilltop is this surreal fortress built by the mad inventor of electrohomeopathy.

The fountain marks the area where hundreds of accused witches were burned at the stake.

2300-year-old Roman road connecting the empire.

A large grotto built in the 16th century amidst Florence's famous Boboli gardens.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

London's smallest police station is barely the size of a phone booth.

France's national museum of scientific and industrial instruments.

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

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

This semi-secret storybook hedge maze is also the oldest garden in the city.

Three bridges and one giant canyon make up this fantastic Spanish settlement.

Architectureal fantasy quarter of Rome.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Museum preserving torture methods from the past.

An unusual round church in London with a Templar past.

An easily overlooked stretch of ornate window fronts and gaslight lamps that could be right from the pages of Dickens.