That Philadelphia is packed with history has never been in doubt: Ben Franklin would be plenty even if the city hadn't been the capital of the United States for a decade, shortly after the ratification of the Constitution.
But all the banner sites tend to overshadow some lesser gems that verge on being swept into historical anonymity.
Fortunately, locals are working to preserve even the most esoteric historical gems. Hidden City Philadelphia runs occasional tours and has a fantastic, frequently updated chronicle of places like the now-abandoned Thomas A. Edison High School and ice factories in the neighborhood of Kensington.
The Association of Philadelphia Tour Guides also hosts a notable look at the city's history: A 12-hour walking marathon held every September that draws hundreds of curious explorers.
Here are just a few of the lesser-known historical places in Philadelphia the intrepid should seek out.