The efforts to decode the mystery of the Antikythera mechanism, a unique machine surviving from around 70–60 BC, extend more than a century since its discovery in an ancient shipwreck off the coast of a Greek island. Although the first experts who looked at the device were baffled by its gear mechanisms, dating, and purpose, this chapter explains how many of these inscrutable aspects slowly came to be clarified and deciphered. The author illustrates the immense efforts it can take to ‘solve’ an enigma: in this case, the combined work of historians, epigraphers, radiographers, X-ray machines, mechanics, filmmakers, and multinational technology companies. The chapter also displays the valuable insights which can come from such endeavours. Decoding the Antikythera mechanism challenged common assumptions about technological skill and astronomical knowledge in antiquity, but it also encouraged innovations in modern technology and revealed something of humanity’s search to understand the cosmos.