The deepest underground city in Turkey was designed to protect 20,000 people behind massive stone doors.

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

Ancient catacombs form the foundation for this Rococo orgy of a church.

Elaborate tile work in this railway station tells the story of Portugal.

Commonly acknowledged as the only public monument to the Devil himself.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

An ancient Egyptian temple in the middle of Madrid, Spain.

A stone slab in Madrid marks the point from which the distances of Spain's national roads are measured.

Over the centuries, this island paradise has done it all, from providing monks with ecclesiastical respite to sheltering an exiled Leon Trotsky.

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

Where commuters walk through remnants of an ancient Greek necropolis.

A two thousand year old brothel uncovered in Northern Greece.

This architecturally eclectic early-20th century mosque was built as a place of worship for the Islamic followers of a Jewish messiah.

What happens when you cross a mayor and a painter?

An Albanian monument to the Communism that nearly crushed the country is now a crumbling wreck.

The most metal church of all time was built in record time because of an international, pious pissing contest.

1513 Turkish world map, full of European state secrets and snarky commentary.

Ancient serpentine sacrifice holder that has stood the test of time.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

A fountain standing as a testament to a doomed alliance.

Five sultans and their families rest in eternal splendor, teeming with overlooked beauty and drama.

A marvel of Byzantine engineering under the streets of Istanbul.