The ruined doorway is a portal to the building's turbulent and torturous past.

The Cycladic architecture makes this Athens neighborhood feel like an island paradise hidden in the shadow of the Acropolis.

The oldest cemetery of modern-day Athens blends the modern and ancient worlds.

The ruins of an ancient Roman tomb hidden in the basement of a trendy clothing store.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

"Holy Wisdom" overlooks the city that became its namesake.

A striking symbol of the Bulgarian capital.

The mysterious, fantastical woodland inspiration for "The Lord of the Rings."

Amsterdam's former hotspot for public executions and dissections.

A Portuguese Jewish cemetery filled with stunning grave monuments that date back to 1614.

A public urinal so pretty, it was declared a national monument.

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

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

This impressive collection of rare books on ancient mysticism inspired author Dan Brown.

The attic of a four-century-old canal house hides a clandestine church.

An ancient passage filled with stalls selling used books, once frequented by Vincent Van Gogh.

This structure atop a craggy cliff in one of the most beautiful parks in Paris boasts an unbeatable view.

The monster at the center of the Darwin Center Spirit Collection.

Mary Kelly was last seen here before she was murdered by Jack the Ripper.

This legendary stone is of unknown origin, and throughout history has been a literal touchstone for British leaders.

Catacombs turned marketplace.

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

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

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