Marco Polo wrote that, even by the late 13th century, the Mongols did not know the location of the tomb. The Secret History of the Mongols has the year of Genghis Khan's death but no information concerning his burial. In the "Travels of Marco Polo" he writes that "It has been an invariable custom, that all the grand khans, and chiefs of the race of Genghis-khan, should be carried for interment to a certain lofty mountain named Altaï, and in whatever place they may happen to die, although it should be at the distance of a hundred days' journey, they are nevertheless conveyed thither."