The World's Hardest Puzzle

In 2012, a mysterious organisation known as Cicada 3301 announced itself on the message board, 4chan. The cryptic post appeared online, seeking 'highly intelligent individuals.' What followed became known as the hardest puzzle on the internet. One that took players across the internet and into real-world locations. After two years of enigmatic posting, it disappeared - and was never seen again. The final puzzle was never solved.