The Nuclear Fallout Zone a.k.a the Radiation Zone is a boundary location that is found in both Navezgane and a random gen world.
The Nuclear Fallout Zone a "edge of the map" style area. How these areas came to be was due to a last attempt to destroy the infection by launch nuclear bombs. But the efforts by the military only worsened the virus causing mutations to occur as well as trapping survivor within the still inhabitable areas. This area can be found at the very edge of the map in a red circle. Players can easily tell were the area is by noticing green patches littering the land. Entering this area is absolutely pointless as there is nothing worth finding, unless one is clever enough to find a full high level hazmat suit and carrying a bunch of health kits.