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

This beautiful Victorian ironwork masterpiece was built to keep London from smelling like poop.

This hidden rooftop garden in downtown London offers a quiet respite from a bustling city.

Public access to clean drinking water was an instant hit among the masses.

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

"Purveyors of traditional sweets and vintage treats."

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

This 22-floor tower's Skydeck offers panoramic views of Amsterdam.

An all-American grocery store in Paris sells U.S. "cuisine" like Pop-Tarts and Heinz ketchup to homesick ex-pats.

135 bronze medallions mark a French meridian line which once rivaled the hotshot Greenwich timeline.

Noirish green neon marks the location of one of the oldest private detective agencies in France.

Down a cobblestone alleyway is a museum dedicated to Romanticism, with a secret garden.

Long-abandoned art nouveau baths beneath Milan's Piazza Oberdan.

Renaissance hospital featuring a rotating door into which unwanted babies were dropped.

The final resting place of the poets Shelley and Keats.

The skull of the patron saint of lovers lies in the Basilica di Santa Maria in Cosmedin—maybe.

Pilgrimage site for star-crossed lovers.

The oldest pub in Ireland may also be the oldest surviving bar in the entire world.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

One of only two commuter aerial tramways in the United States.

The granddaddy of all tourist traps, built on ice water, jackalopes, and a giant dinosaur.

A sculpture made of 10 Cadillacs as a monument to the "Golden Age" of the American automobile.

One of the most scenic stretches of road in America winds between some of the country's oldest trees.