What is the origin of the idiom "the streets of somewhere are paved with gold" and when to use it?

The idiom "the streets of somewhere are paved with gold" has its origin in the 19th century, when many immigrants were coming to the United States in search of a better life. They believed that it would provide them with instant wealth and prosperity. However, the reality was often very different, and many immigrants struggled to make a living in the new country. Over time, the phrase came to be used to describe a place or situation that is believed to offer great wealth or opportunity, but the reality may be very different.