The dark areas of this map show built-up areas with blank areas for water, parks, streets, etc. Pretty. Here’s what Bostonography has to say about it:
Besides being inconsequential eye candy, though, the map is somewhat useful for interpreting urban geography. Some manmade patterns are much clearer in this map than in an aerial photograph you’d find on Google Maps or elsewhere, which shows all this and more. Assuming some base level of local knowledge (say, where the ocean is), it’s possible to identify various spaces: built-up (gray) versus open (blank) areas, downtown (large, dense footprints) versus residential (smaller, separated footprints) areas, steetcar suburbs (long main drags with density dropping a block or two away) versus more interior urban areas (consistent density and often smaller, straighter blocks), and so on.
Click on the pic for a gi-normous version.
(Source: theersatzvegetarian, via electricfire)