The grey zone is the center of the Travian world. Settling in the grey zone will result in Natars attacking you from each World Wonder Village. 5 of the 13 World Wonder Villages are in the grey zone (plus the Natar capital), plus there are a lot of 50% oases (including wood, clay and iron) and a lot of 15 croppers. However, grey zone villages can only produce culture points using celebrations.
Note: In Ancient Europe Servers 0|0 is Roma of Imperial Rome, Another Npc. The Main Natar Village is at 400|400