An ancient passage filled with stalls selling used books, once frequented by Vincent Van Gogh.

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.

Cold war icon and onetime "hole" in the iron curtain.

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

A tree-like building perches on its trunk in the Steglitz neighborhood of Berlin.

A marine aquarium with an astounding variety of fish hides in the basement beneath the famous Palm House.

The beloved beast's taxidermy remains sit in the Natural History Museum's cafe.

The bridge is a secret gallery of discarded gum that has been transformed into miniature masterpieces.

A mysterious shape catches the eye in this 16th-century painting.

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

A statue of the legendary Celtic warrior queen who fought the Roman invaders stands in one of the cities she once destroyed.

This former medical factory gives home to cutting edge arts in the shadow of a gas works.

The last four extravagant street signs of London's historic banking street.

You'd never know the houses at 23-24 Leinster Gardens were fakes—until you see the train tracks on the other side.

Bronze sculpture celebrating the relationship between Churchill and Roosevelt.

19th-century scientists would make the pilgrimage here to verify the precision of their measuring sticks.

This London plaque marks the spot where David Bowie's famous alien made his debut.

The Metropolitan Police refurbished the blue box (perhaps not coincidentally) the same year "Doctor Who" returned to TV screens.

A charming 17th-century alley is lined with secondhand bookstores and antiquarian shops.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

This emotive sculpture was originally created for the 1878 World's Fair.

It appears as if a man is standing behind this giant airport clock, painting the hands in real time.

London's amazing modernist public square that never was.

A famous burial ground with a history both grim and literary.