999 stairs lead visitors through a massive hole in a mountain known as the Gateway to Heaven.

The world’s tallest outdoor lift stretches along the stone pillars that inspired the floating mountains in the movie “Avatar.”

The strange phenomenon causing gravity to "work backwards" on this hill has been blamed on the paranormal.

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

A kaleidoscopic warehouse-maze of handmade neon signs.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

A jaw-dropping "megalibrary" that turns book-browsing into a geometric adventure.

Step into a pastel time capsule where candy is truly dandy.

Alexander Hamilton’s creation caused quite a bit of controversy.

A tour de force of a fountain, memorializing a man who loved fountains more than anything else.

This elaborate towering structure was once famed for its revolutionary height.

The first American department store, and home to the largest operating musical instrument in the world.

Dr Barnes' $25 billion private collection of art and arboretum.

Mural made of 100,000 pieces of hand blown glass, and until recently, the largest glass mural in the US.

Philadelphia boasts one of the best — and most often overlooked — traditional Japanese gardens in North America.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

This classic restaurant features a gorgeous mirror-clad room.

Taste freshly foraged yarrow and black locust blossoms at this ambitious cocktail bar.

An old tram depot transformed into a vintage car paradise.

The last remnants of a massive medieval wall that once encompassed the city of Berlin.

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

This conical hill was built as a testing ground for an engineer known as the Glider King.

Floating swimming pool within a moored vessel.

The site of the famous Nazi book burning campaign of 1933 remembers its "Night of Shame".