The Independent of London reported that official U.N. figures show that throughout the world, urban populations have more than quadrupled over the past 50 years.

London, 200 years ago, became the first city in the world since ancient Rome to reach a population of 1 million. Now, according to experts, about 200 cities boast a population far more than 1 million, the Independent said. Tokyo, known as a "metacity," has a population of 20 million.

Reports on the increase in urban populations are scheduled to be published over the next few months, the newspaper said.