Entering the Hall of Mirrors is a highlight for every visitor, but there is a hidden, almost high-stakes spy story behind its beauty. Completed in 1684 by architect Jules Hardouin-Mansart, the hall features 17 massive arched windows reflected by 357 mirrors. At the time, Venice had a total monopoly on mirror glass, and the technology was a closely guarded secret. To build this hall, French agents had to secretly lure Venetian artisans to France. The Venetian government was so furious that they reportedly sent assassins to try and kill the defectors in what some call the Bloody Mirror war. This hall was also the site of massive historical shifts. In 1871, after France’s defeat in the Franco-Prussian War, the German Empire was actually proclaimed right here. Decades later, on June 28, 1919, leaders met in this very room to sign the Treaty of Versailles, which officially ended World War One. A quick tip: as you walk into the hall, keep moving all the way to the far end before you stop to look back. You will get a much better perspective and a much clearer view for your photos.