The city's power brokers have long shared stories inside the gilded halls of the Union League. Few of them, though, could match the drama of this:
"I saw Booth move his hand to his side and pull a knife."
"I looked down at him and he stopped as he says "I have done it," as he shook the knife."
That is the only firsthand account of Abraham Lincoln's murder, by a man who saw John Wilkes Booth shoot the president then pull a knife on the first lady.
It is stored for the ages. Along with it, a piece of the undershirt Lincoln wore when he breathed his last, the only known to remain in the world.
Just blocks away, but by no means easy to get to, is the treasure trove beneath the Historical Society of Pennsylvania, including the earliest draft of the United States Constitution.
As in the very first, from 1787, and it is incredible. Instead of "We the People of The United States" this one begins "We the People of the States of Massachusetts, New Hampshire, Rhode Island..." It lists all 13 states.
And it suggests a different name for our country: The United People of the States of America.
But while all the hidden treasures are historic, some are also somewhat odd.
Inside a book, deep within the walls of the Academy of Natural Sciences, there are tufts of hair, willingly cut from the heads of the first 15 Presidents.
While in some respects a novelty, it could someday unlock the secrets of how they thought.
Over at the Eastern State Penitentiary where inmates were once locked in, the public is now locked out of certain sections, the medical wing among them. It is a sprawling complex built to battle Tuberculosis which killed more prisoners than every other illness combined.
And then there's the basement vault at the Mutter Museum called the bone room.
Only 12 percent of the museum's holdings can be seen by the public, the rest are housed there: skeletons, even preserved organs of thousands of the deceased, ostensibly for medical history and modern research.
Then we found the very sword Ben Franklin wore at his side, locked away in the vault of the Franklin Institute. Along with one of the inventor's most famous creations, the lightning rod; the particular one seen in our report was struck twice.
For even more of Philadelphia's hidden treasures, visit this page.