Beyond an unassuming brick archway on Market Street is the site, if not the structure, of Ben Franklin's Philadelphia home. The original dwelling was razed in 1812. All that’s left is an archeological dig–looking foundation and the modern steel frame "ghost" girder meant to represent the original house and adjacent print shop. The real story is underground in the Benjamin Franklin Museum—completely renovated in 2012–13 and re-opened Aug. 24, 2013—that cleverly outlines Franklin's irrepressible ingenuity.
Though small, the museum is pretty exhaustive, with sections on every aspect of America's favorite Renaissance Man: His family life and household, scientific inquiry and inventions, civic improvement initiatives (he started the country's first volunteer fire department, lending library, fire insurance company, public hospital, and non-sectarian university—we call that last one "Penn"), and his careers as printer, businessman, diplomat, politician, and revolutionary of a satirical bent.
The museum includes some of Franklin's lesser-known, more offbeat inventions, such as bowls for a glass armonica (played like water glasses at the dinner table—there's a digital touchscreen version next to it you can play), his own carriage odometer (a device he invented to calculate distances between post offices when he was Postmaster General), and replicas of wooden swim fins. (Franklin was a champion swimmer. He also invented kite surfing. That sounds like a joke, but it isn't.)
There are plenty of interactive exhibits—both of the old-fashioned "please touch" variety and the new-fangled touchscreen. The puzzles shout "huzzah" when you solve them. Screens loop quirky, Monty Python-esque animations that illustrate several classic Franklin anecdotes (love the one with him and John Adams in nightgowns and stocking caps, forced to share a bed during a road trip and arguing over whether it is healthy to sleep with the window open; Franklin bores Adams to tears with his droning theories.)
Back upstairs, take the time to pop into the other two (free) Franklin Court sights: a replica printing office in one of the Market Street buildings Franklin used to let out; and the still-active Franklin post office, where Franklin served as the nation's first Postmaster General, and where all mail is still hand-canceled. Fun fact: This is the only post office in the U.S. that does not fly an American flag—since none existed when it first opened in 1775.