Some features must remain unchanged:
- Canyons/Rough ground
Now rivers might conceivably be dammed and I might drain the occasional lake, and a new desert (or crater) might have sprung up in the last few thousand years, but otherwise this stuff stays the same. I know rivers can change course but I'm not going to do a lot of that just for sanity's sake as it eventually weakens the advantages of using an existing map.
Some things must be different
- Place names
- Cities and towns
This is not a PA game like Gamma World of Mutant Future where names like Pitz Burke and Mecksgo are part of the fun. I don't want my players to figure this out for a while so regular D&D/Fantasy names are essential. There won't be any stop-sign shields or coats of arms based on the American flag either. OK there might be a little of that but not enough to set off any alerts.
Similarly civilization has completely collapsed and sprung up so that there has been no continuous habitation by organized cultural groups in set locations. Thus cities and towns are all new. The locations aren't necessarily new - a good city site is a good city site - but the inhabitants do not think of it as "Pensacola" or "New Pensacola" or "Penzkolar" or "Prince of Kola" or anything similar. They call it Baytown or Dukesberg or something relevant to them, not something relevant or reverent to societies of the past that they are completely unaware of. So there can be no recognizable places or names on the map. (though I kind of like Penzkolar - maybe in the next Mutant Future campaign)