Mississippi River Delta. Stolen from Google Maps.
Try this. Get in your airplane (poor man's equivalent: load up Google Maps). Go to Baton Rouge. Now follow the river as it winds south. The evolution is spectacular.
What surprises me more is that there are (or were) roads and towns out there.
Also, Flickr's geotagging interface is exciting: you can browse a map and find photos taken at a given location. This is exactly what the GeoWiki was to be, but with wiki snippets instead of just photos. (GeoWiki became BerkeleyWiki became RocWiki.)