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

The oldest operating Mississippi River–style steamboat still navigates the Ohio River.

A historic Georgian building and warm springs.

The oldest of the three remaining bridges in England with buildings on top of them.

This legendary stone is of unknown origin, and throughout history has been a literal touchstone for British leaders.

These 90-year-old murals of local kings, Vikings, and outlaws hide in plain sight in a beautifully baroque shopping arcade.

Exquisite carvings of leaves, Green Men, and the occasional dragon adorn a medieval chapter house.

Legend says this demonic carving inside a medieval cathedral was one of Satan's minions.

Murals of the wild parties once held on the frozen River Thames.

Buried for centuries, this hidden cellar is all that remains of London's medieval Whitefriars Monastery.

An engineering error ensured this cavernous 350-foot-long subterranean thoroughfare was never used as intended.

These official units of measurement—including chains and perches—lie hidden beneath tourists' feet in a popular London hub.

The fierce beast perches atop a pedestal marking where the historic City of London gates once stood.

A 300-year-old tea shop that brought tea to the English people, not to mention the Queen herself.

This pump on the bad side of Victorian London betrayed a horrifying revelation about the water supply.

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

A curious urban windmill once owned by a renowned British mathematical physicist.

The Birthplace of the Englishman who founded the A.C. Milan football club.

London's smallest police station is barely the size of a phone booth.

The Midwestern United States' tribute to Michelangelo is a foam statue sprayed with gaudy gold paint.

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

Left by the Devil, an ancient quarry or just plain old erosion, this enigmatic rock pillar rises 28 feet from the hillside.

This otherwise ordinary close on the Royal Mile constituted the end of the world for Edinburgh’s poorest residents.

Children's hospital in London that operates on royalties received from Peter Pan, which J.M. Barrie signed over in 1929.