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.

The ancient Greek Titan guards this massive dam holding a lightning bolt to symbolize electricity.

Religious structure known for its sculpted details.

This massive underground salt mine now holds a sci-fi theme park in its depths.

This Transylvanian church has changed its denomination four times.

A memorial museum to the political prisoners who were held at Sighet Prison, once one of the most feared places in Romania.

The venerated body of a 12th century saint is celebrated each year with the 'Race of the Candles.'

Be(w)ar(e) the moat around this historic Czech castle.

This town named for the ancient God of War is home to fewer than a thousand people, but it's the birthplace of the Greek Revolution.

This legendary city has been a tourist attraction for centuries.

The secular incarnation of a religious meditation.

The historic tower houses of this nearly abandoned Greek town have been compared to the spikes on an iguana's back.

Seventeen oak trees sprout from the roof and walls of this tiny chapel without any visual evidence of roots.

The hallucinogenic center of the ancient world.

This exclusive resort has completely covered a tiny Balkan island in a 5-star warren of guest rooms.

A musical instrument played by the sea.

A tiny church on a man-made island in the Adriatic.

A curious cave church carved into the face of a cliff.

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

Thousands of tourists and residents in Cologne affix "love padlocks" on the Hohenzollernbrücke Bridge to symbolize their affections.

Be it nature, art, or abandoned military architecture this eclectic German "museum" has you covered.

This futuristic German television spire is actually the world's largest digital clock.

Twisted buildings adorn the banks of the Rhine river.