I have a nuvi 205 and a couple others. Haven't looked at the map in question, but with detail set to "most" you will see ALL map details until you zoom out farther than 1.2, or possible 2 miles.
This series has the worldwide routable DEM basemap. It normally doesn't show with City Navigator enabled until you zoom out pretty far - like 20 miles - and then it will add DEM shading to the map. If you turn off City Navigator you will see the basemap, but again I think you have to zoom way out before the DEM shading kicks in. There is no control to turn the basemap off, but I suppose you could delete the gmapbmap.img file. Not sure if this would cause some other bad thing to happen.