A treemap of a highly complex dataset always looks mesmerizing, even when the rectangles seem to have peculiar shapes. The project with the apt title "You're looking at $480M of Groupon's gross revenue" by Paul Butler [paulbutler.org] makes true on its promise in the title: based on an internal Groupon memo that was recently released by the Wall Street Journal, it displays the performance of the historical deals at the deal-of-the-day website Groupon for the top 20 cities in the U.S.
Each rectangle represents one Groupon deal. The rectangle's width represents the price, while its height represents the number sold. As a result, the surface area represents the total gross revenue.
Do not forget to scroll.