(IDEX Online) - Sotheby's Geneva is to auction the ultimate bicycle, decorated in gold leaf and embedded with a 2.03-carat round brilliant-cut Fancy Brown-Yellow diamond at the top of its steering tube.The estimate has not been disclosed, but the opening bid in an online auction (closing 18 May) is for $67,000.Colnago, the iconic Italian racing bike firm, has produced the one-off bike to mark the 106th Giro D'Italia, the three-week 2,142-mile road race that will end on 28 May.Forty-nine other carbon fiber Colnago Gioiello C68 bikes are also being made, with the gold leaf, but there's only one Colnago Gioiello Numero 1, with the diamond."The Gioiello's frame is carefully enveloped entirely in gold leaf, expertly applied by skilled Colnago artisans, resulting in the shimmering and regal aesthetic," says Sotheby's."Each delicate application of gold leaf contributes to the uniqueness of every Gioiello."The round, brilliant-cut 2-carat diamond, shining in a Fancy Brown-Yellow Colour plays with the hues of the surrounding gold making this true art piece the ultimate luxury item."Pics courtesy Sotheby's