Ben Fry's classic map of the United States,
demonstrated that a complete map of streets also
implicitly creates a map of the topography around them,
because the form of the land determined the locations of the roads.
Few places in the world show this effect as strongly as
Japan, where intensive urbanization constrasts sharply
with the surrounding rugged terrain.
Even though Japan has been thoroughly mapped in OpenStreetMap
for several years, the map continues to be refined every day.
Only a handful of roads, shown in blue, have been untouched
since 2007. The other colors progress in time from purple in 2008
through red in 2010 and orange in 2012 to yellow roads that have been
edited in the past year.