This Roman arch marks the location of an ancient gate at one of the Seven Hills of Rome.

Installed in an act of one-upsmanship, the annual sundial in this church is also a symbolic victory for the Gregorian calendar.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

Jesus' footprints and the first catacombs in the world.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

A monument to the three wars that led to German unification towers within a Berlin traffic circle.

Reminders of the Battle of Berlin still scar the railway.

A replica of the Liberty Bell rang daily from West Berlin's City Hall throughout the Cold War.

Beneath the impressive baroque cathedral that rises from the center of Berlin lies the largest collection of Prussian royals in the world.

A restaurant and observation deck built in a unique broadcasting antenna.

On the Spree bank, discover one of the last reminders of a symbolic wall that divided, and was torn down by the people.

Art and a pun, all in one.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

A narrow passage next to a cafe leads to a courtyard exploding with murals, tags, and paste-ups.

These ornate arches show how the course of the River Thames has changed.

Several plaster noses are hidden in plain sight around London's Soho neighborhood.

This once-controversial and slightly confusing statue of Achilles was built out of captured cannons.

A unique tribute to the millions of animals who served and died for the British military.

London's last remaining public soapbox site has seen speeches from Karl Marx, Vladmir Lenin, and George Orwell.

Never actually a tree at all, this spot was the site of London's public hangings for nearly 600 years.

The final resting place to 300 Victorian-era pets hides inside the city park.

Legend says these colorful, invasive residents are the descendants of birds released by Jimi Hendrix.

This long-hidden space above Westminster Abbey now displays the battle gear of the legendary King Henry V.

The broken skateboards that became a poignant memorial to a murdered skater.