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

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

A small etching on the white marble parapet was written in runic script by a Viking mercenary.

A marvel of Byzantine engineering under the streets of Istanbul.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

St. Mary's features one of the most spectacularly decorated cathedral interiors in all of Europe.

Beneath Kraków Old Town's main square lies a hologram-filled medieval market vampire graveyard wonderland.

A set of ancient drawings in the desert of Peru that are so massive, many of them can only be fully seen from the sky.

Situated on a sacred Inca site, this 16th-century cathedral took nearly 100 years to build.

This geometric feat is a testament to the Incas' mesmerizing architectural abilities.

A painting in the historic Cathedral Basilica depicts Jesus and his disciples dining on a traditional Peruvian menu.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

Rare collection of medieval books under lock and key.

The largest known medieval map of the world.

If you look closely at the oldest bridge in Paris, you might notice hundreds of ugly faces leering from its sides.

Created hundreds of years ago, the magical follies and landscapes at this park were almost lost to time before being restored.

This whimsical, unique clock has been entertaining shoppers for well over 20 years.

This tranquil churchyard in the heart of England’s mining country whispers tales of both triumph and tragedy.

A replica of one of the most complete mammoth skeletons discovered in England.

This mysterious underground cave in Shropshire dates back to the 18th or 19th century.

This charming railway is one of the oldest and steepest funiculars in England.

There's a labyrinth of manmade tunnels stretching for over an acre beneath Bristol.