This ancient theater was once the home of fierce gladiatorial battles.

The world's tallest bridge is also possibly the most elegant.

The only remaining collection of flayed figures made by French "madman" Honoré Fragonard.

The largest underground church in Europe.

For hundreds of years, automatons moving to metallic music have been marking the passage of time.

An icy lake tucked among jaw-dropping alpine panoramas.

This French ghost town from World War II has been left as a memorial to German atrocities during World War II.

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

A private garden of sculptural eccentricities.

One man's desire to transcend art led to the construction of this outsider chapel.

A saintly relic hidden in a Prague church basement.

The slender brass strip in Prague's Old Town Square was used to tell time from 1652 to 1918.

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

This little-known relic crypt holds stolen parts of a Roman Empress.

This modern museum of Mediterranean culture is surrounded by a surreal concrete honeycomb.

The world's largest reflecting pool is just two centimeters deep.

Elevated freight railway turned wildly successful urban park.

Macabre astrological automaton clock dating to the late 1400s.

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

The pile of books behind the dignified writer gave the statue a most undignified nickname.

Go inside to really appreciate this 500-year-old technological masterpiece.

This community on a small Venetian island has taken to painting their houses in bright neon hues.

Visitors dating back to the 1600s carved their marks in the stones of the iconic tower.

There has been an astronomical clock on this spot since the 14th century.