A mass grave for victims of one of the city’s worst fires.

A curious friendship between two inanimate ladies.

A way to take your secrets to someone else's grave.

A real flying saucer, contracted by the U.S. Air Force.

You can walk through the first Boeing Air Force One, which famously carried JFK's casket from Dallas back to D.C.

Intricate storybook scenes are tucked inside these shadow boxes, which are tucked inside a library in the Pocono Mountains.

This might just be the TARDIS of bookstores.

The oldest of only three existing statues of the great novelist stands in a city he did not care for.

Enjoy a slice while browsing the world's largest collection of pizza memorabilia.

An Irish Memorial commemorating those who perished due to potato blight.

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

The sounds of the world's largest fully functioning pipe organ dazzle shoppers at a Philadelphia Macy's.

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

This meticulously extracted nervous system allegedly came from a 19th-century custodian who donated her body to science.

Yo, Adrian!

A clone-tree in Washington Square Park sprung from seeds that went to the Moon and back.

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

This little-known collection holds everything from "Dracula" notes, to the manuscript of "Ulysses," to the forged works of Shakespeare.

This Philly cemetery is the eternal home of many famous area residents, including Rocky Balboa's wife.

Tour the dark and beloved poet's former cobwebbed basement, which may have inspired "The Black Cat."

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

The taxidermied remains of Charles Dickens' pet raven, which helped inspire one of Edgar Allan Poe's most famous poems.

Huge masonic hall in Philadelphia with lavishly themed rooms.

Mural made of 100,000 pieces of hand blown glass, and one of the largest glass murals in the US.