Cartogram

http://www.spatialanalysis.ca/2011/exploring-germany-through-cartograms/

A cartogram is a type of map in which some type of thematic variable is visually substituted for distance or land area. The space within the map is purposefully distorted in order to visually show the intensity of the thematic variable. Cartograms help to show concentration of populations spread over land masses so that the general viewer can observe concentration accurately for when the size of a seemingly tiny piece of land is much more heavily populated and must not be ignored or deemed statistically insignificant. The map shown above shows a side by side comparison of a choropleth map of population with that of a cartogram to exacerbate the importance of the distribution of the German population in city centers.