"London streets are paved with gold" is a saying that came from the 19th century story Dick Whittington and His Cat, loosely based on the 14th century Lord Mayor of London, Richard Whittington.
The saying, which expresses the idea of a "land of opportunity", is partly ironic, since Dick Whittington found when he went to London that the streets were in fact grimy and poverty stricken.
"[2] The Leisure Hour (1866) wrote that "The rural poor grow up (we are told) with the notion that London is a mine of wealth — that its streets are "paved with gold;" and their heads are full of traditions of pennyless youngsters getting on in London until they become men of fortune.
(International Standard Version)[4] The term also appears in John Bunyan's Pilgrims Progress (1678).
His Celestial City is described as: "builded of pearls and precious stones, also the streets thereof were paved with gold" Pilgrims Progress, John Bunyan, 1678 http://utc.iath.virginia.edu/christn/chfijba6f.html