Mumbai is the 5th largest megacity in the world. Which is the largest urban aglomeration?

Here is the order of the top 5 largest cities: Tokyo, Japan Guangzhou, China Seoul, South Korea Delhi, India Mumbai, India Mexico City, Mexico There are many places that have the lists. Some are: http://millenniumindicators.un.org/unsd/demographic/sconcerns/densurb/densurbanNotes.htm http://www.city-infos.com/list-of-megacities-2011/ http://en.wikipedia.org/wiki/Megacity http://en.wikipedia.org/wiki/List_of_cities_proper_by_population