Cities will become rich, diverse mines of raw materials.

Jane Jacobs : writer, Activist
"In the highly developed economies of the future, it is probable that cities will become huge, rich and diverse mines of raw materials. ... The largest, most prosperous cities will be the richest, the most easily worked, and the most inexhaustible mines. Cities that take the lead in reclaiming their own wastes will have high rates of related development work."

Jane Jacobs, The Economy of Cities. New York: Random House. 1969.