This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

Elevated freight railway turned wildly successful urban park.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

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

This historic observatory contains the world's oldest refracting lens telescope.

Berthed at the Charlestown Navy Yard in Boston, "Old Ironsides" is the oldest commissioned warship still afloat.

This monument on Breed's Hill proves that one of the most famous battles of the Revolutionary War is misnamed.

The American Revolution was galvanized into serious action due to the tragic clash with British soldiers that occurred at this location.

Narrowest house in Boston.

The site of one of the strangest disasters in history—a wave of deadly molasses traveling at 35 mph.

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

Thanks to modern navigational tools we now know that the true prime meridian runs through a park next door.

This massive collection of British military artifacts includes the heartbreaking personal letters of the men in the trenches of WWI.

Pop culture has helped to keep this iconic British building from being destroyed.

One part local history, 99 parts gruesome haunted house.

An unusual round church in London with a Templar past.

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

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

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

Started as a kitchen garden, now the second largest botanical garden in the world.

Outdoor art exhibition made of classic Tetris pieces.

Come for the flowers, stay for the bats!