In the 12th and 13th Centuries he defeated the most advanced empires of his time: the Shah of Khwarizm in the Middle East, the Sultan of Delhi and the Chin Empire in China. From eastern Asia his generals conquered the wealthy principalities of Russia. They pressed on as far as Hungary. The booty yielded by his conquests was incalculable.
When he died in 1227 he was, according to legend, entombed by 2,000 servants, who were killed so that they could not reveal the site. Ancient Mongol accounts add that the 800 soldiers who killed the servants were also killed, to preserve the tomb's secrecy.
On Tuesday a Chicago commodity broker and amateur historian said he had signed an exclusive contract with the Mongolian Academy of Sciences to search for the tomb and the treasure. 'I believe there is lying in the ground with (Genghis Khan) the greatest unretrieved treasure-trove in the history of the world,' said Maury Kravitz, 62, at his office in the Chicago Mercantile Exchange.
He said that at first the Mongols did not know what to do with the cities they had conquered. Later, 'they removed anything of value from the cities. From 1212 through to Genghis's death on 18 August 1227 there was a constant flow of treasure back to Karakorum, the imperial capital. Not one single piece of that wealth surfaced. It is fair to assume, given the size of the burial party - 2,000 excavators and 800 soldiers, - that it was all buried. It would be a hundred Tutankhamens in one.'
Mr Kravitz hopes to launch an expedition next spring. In summer Mongolia is baking hot. The winters are severe, with temperatures dropping to -45F and deep snow. He recently returned from Mongolia, after persuading the government that he alone knows the location of Genghis's secret tomb. He believes it is in the Burkhan Kaldun mountains in Hentiy province, east of Ulan Bator. It is a remote area, with no roads. 'The final pieces of the location came to me in Mongolia 14 days ago,' he said. The government has granted him exclusive rights to the search.
'This is not a treasure hunt, this is a histo-geographic expedition. This is not to probe around looking for buried gold . . . It's an expedition to deal with the gaps in the history of the Mongol imperial period. National Geographic called this 'the last great expedition of the 20th Century.'
Mr Kravitz said that a three-year Japanese expedition had returned in 1992 after finding hundreds of tombs. But they were all from a later period and none belonged to Genghis. After years of study, he says he knows where to find 'the Great Khan'.
Born between 1155 and 1167, the 'Khan of Khans' was first named Temujin, meaning 'blacksmith'. With a combination of military genius, diplomacy and cunning, he united the Mongol tribes and carved out the greatest empire in history. His armies could have continued into Europe. According to the Secret History of the Mongols, he fell from a horse during a hunt. Had he not, his generals might have sent their disciplined armies against Europe's feudal levies. Instead they turned back to settle the succession.
According to the few accounts of his life, in his later years Genghis Khan was counselled by Buddhist shamans and later by a Taoist sage, Ch'ang Chun. The Taoist urged him 'not to desire the things that other men desire'. Genghis told his sons and other princes that Ch'ang Chun was from heaven and that they should engrave his words on their hearts. Judging by his penchant for food, drink and women, he did not engrave them on his own.
'We're talking about Samarkand, Bukhara, Tashkent, northern China - the most advanced civilisations in the world', Mr Kravitz said. 'It would certainly take care of Mongolia's foreign exchange problems for the next several hundred years.'