One of the most secretive and inaccessible places in the world is not a supervillain’s lair carved into an active volcano, or a hidden chamber where black magic and other nefarious rituals take place. Rather, it’s a … well, it’s a library. A church library. The Vatican Archive, according to Mental Floss, is, on the surface at least, a place where the personal records of the pope can be archived and stored. However, it’s also a repository of so many documents that the shelves alone, if laid end to end, would stretch 50 miles.

The Vatican has been extremely cagey about what’s inside those documents, although over the centuries, it’s revealed a bit about what’s in there. While those hoping for documented proof that, say, aliens built the pyramids, are going to be disappointed, there are some priceless historical treasures contained within, such as the papal bull excommunicating Martin Luther, and letters from Abraham Lincoln and Jefferson Davis to Pope Pius IX.

The oldest document — that we know of — in the Vatican Archive may also be its most mundane. It’s in no way connected to any major historical event, and is instead a routine record of a rather commonplace activity.

A 1,200-year-old receipt

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