One of the most famous tales in the Histories of Herodotus is that of the Persian conqueror Cambyses (525–522 BC), son of Cyrus the Great, who sent an army across the desert to destroy the Siwan Oracle. According to Herodotus, the fifty thousand-strong army marched from Thebes (Luxor) for seven days to an “oasis”, and thence towards Siwa – which leaves room for doubt as to whether the oasis was Kharga or Farafra. Depending on which you favour, their last watering hole was Ain Amur or Ain Della, beyond which the army ran out of water and perished in the Great Sand Sea after a sandstorm scattered and buried the weakened troops. Some ascribe this disaster to the Persians miscalculating their longitude; others blame their ignorance of the hostile environment. The mystery of where the Lost Army disappeared tantalized explorers such as Almássy, who claimed to have found the site but never disclosed its location. In 2001, an Egyptian professor announced he had found it after discovering bronze arrowheads and human skeletons north of the Al-Ubayyid Cave, but failed to convince anyone; in 2010, two Italians claimed to have found Persian armour, but were denied permission to excavate. Others theorize that the army numbered far less than fifty thousand soldiers (Persian sources routinely overestimated the size of armies), and was in fact perhaps no larger than five thousand.