It shows just how remote each place on earth is. A dark area means it takes more than a few hours to reach a city of 50,000 or more by overland (or boat) travel.
Click on the map to read a longer article about the map on New Scientist.
I’m fascinated by this map because I spent two months traveling across the Amazon basin in 2006, and I’ve been trying to convey just how remote this region is. Now I have this map to help!