I must have a different version. My Edge 705 has Settings>Map and then a "detail option", where it is set to "most" detail. No detail at all though.
I have a 4GB card. I downloaded the map to the SD card via the Garmin website (Garmin Connect?). The SD card has a 485MB file named gmapsupp.IMG and a also a file named gmapsupp.unl but it has zero KB. I also wasn't aware I had to unlock the map. Maybe it didn't download correctly?