This super steep hike ascends 2,000 feet in less than a mile.

The largest free-standing aquarium in the world resides in a hotel lobby in Berlin.

A bronze plaque marks the site of the only show the "King of the Soul Singers" ever missed.

Home to a protest movement, a bombing, and a dramatic change in labor history.

This historic hotel invented the chocolate brownie.

A spectacular remnant of an Adler and Sullivan masterpiece that was destroyed in 1972.

Once at the center of U.S. finance, the historic Trading Room was meticulously recreated piece by piece and rebuilt in the Art Institute.

Each of these gorgeous, intricately decorated rooms is painstakingly crafted to the scale of 1 inch: 1 foot.

These pretty kitties killed and ate as many as 135 railway workers.

At Chicago's revered Field Museum, visitors are invited to learn about and literally explore DNA.

Where dioramas can follow you home.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the first ‘Harry Potter’ film.

This coffee shop lies hidden beneath a historic church.

Claiming to be the oldest hat store in the world, this historic haberdashery had a hand (and a head) in the creation of the Bowler.

The John Snow Memorial marks the epicenter of London's 1854 cholera epidemic.

Tourists who rely on a transit map to find the iconic Beatles location often end up in a far-off neighborhood.

The bones of two medieval royal lions were discovered at the historic fortress.

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

A community of artists and entrepreneurs seeks a simpler life on London's waterways.

A labyrinth hides in plain sight at each of the city's 270 Tube stations.

Scattered throughout London are ancient remnants of the city's former bounding wall.

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

The last remaining example of the boatmen's perches that once dotted the south bank of the Thames.

Richard III supposedly disposed of his nephews' bodies here in an effort to seal his claim to the throne.