With the first ever World Cities Day taking place on Friday, the Guardian is partnering with UN Habitat for the Cities Day Challenge, a day-long competition where representatives of 36 cities around the world will present their best city ideas, with the winner being selected for an in-depth article in the Guardian. Judged by Ivan Harbour of Rogers Stirk Harbour + Partners, Toronto City Planner Jennifer Keesmaat; Anna Minton, Dan Hill, Usman Haque and Adam Greenfield, the Guardian will be live-tweeting the entire day.
They are also reaching out to readers to "share your photos, videos and stories of something brilliant that your city does better than any other," some of which they will feature throughout the day. You can follow this link to contribute - or read on after the break as we take the opportunity to round up some of the biggest city ideas that have passed through the pages of ArchDaily.
