Northern Ireland's Brobdingnagian stepping stones.

Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

This historic covered bridge contains a series of macabre paintings that communicate one thing: everyone dies.

This sweet-toothed bear searching for snacks has been a symbol of Madrid for decades.

An 18th century wonder of the world, lost in WWII, re-created at the Catherine Palace.

This pirate-broadcasting-tower-turned-restaurant played a rebellious role in the history of Dutch television.

The only museum with its curator—and her pets—buried inside.

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

The oldest operating pharmacy in the world features 800-year-old recipes.

A hugely vast Irish landscape of barren rock that stretches for miles.

This single room has survived the centuries with almost no deterioration.

This singular Irish dolmen is more Frank Lloyd Wright than upright stonehenge.

The ancient tomb acts as a calendar that keeps perfect time.

One of Ireland's most infamous prisons for rebels including men, women and children.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

Hungarian Jews were ghettoized during the Second World War, but little remains of the original wall that closed the Jewish people off from the rest of the city.

The metal leaves on this tree are engraved with the names of Holocaust victims.

A random tree outside a Budapest hotel has become a DIY shrine to the late singer.

A Trabant car, a kangaroo statue, and a plethora of plants take over this abandoned-factory-turned-bar.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

This bridge was constructed from the rubble of the infamous Bastille.

A 16th-century fountain marks the site of a lost medieval cemetery once filled with mass graves.