Up for a challenge? An antiques marketplace is offering $1.2 million (£1m) to the first person who can prove the mythical Holy Grail exists. The stuff of legend, the chances of discovering the chalice used in the Last Supper are on a par with finding a pot of gold at the end of a rainbow, but that won't stop some people. Treasure hunting is all the rage right now and metal detector sales are booming. From Nazi gold to missing Fabergé eggs, we take a look at the most epic treasure hunts ever.