Lyon, France is home to two remarkably preserved Roman theaters, one dating back to 15 BCE.

The largest underground church in Europe.

This natural French spring has been turned into a magical grotto by Roman and medieval constructions.

Ancient paintings known as the "Sistine Chapel of Cave Art."

The subterranean "lake" below the Paris opera house inspired the Phantom of the Opera's lair.

Sacked by Vikings, blessed by William the Conqueror, dealt a fatal blow during the French Revolution—these ruins have seen it all.

A mechanized clock where a man fights off a dragon, crab, and rooster.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

Martin Bricelj Baraga's monolithic sculpture measures the blueness of the sky, and changes color to match it.

A trough of 700 strange bronze faces runs through a narrow alley in Ljubljana's old town.

An otherworldly alpine pasture with its own unique microculture that recalls Middle Earth.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

This one-time health resort was used by aristocrats around the world.

An ancient capital city that dates back 3,000 years old and harbors many surprises.

In this desolate valley resides a gorgeous set of rocks sporting a technicolor design.

Rocky Atlantic beach home to a stunning stone arch.

One of the most well-preserved temples of ancient Egypt.

These Egyptian statues have survived for 3,400 years and were an acoustic wonder of the ancient world.

Some believe that this ancient mural depicts technology far ahead of its time, but in reality it's nothing quite out of place.

More than 100 monumental tombs carved into rock are preserved at this ancient Nabataean site in the Arabian Desert.

An unfinished tomb carved into a giant boulder in the Arabian Desert.

This impressive system of tanks was used to store drinking water as long as 2,000 years ago.

One of Yemen’s oldest and most beautiful mosques was named for the incredible, historical queen buried inside it.