Neutral zones are areas between the borders of two or more countries that have been intentionally left unoccupied for a political reason (often occupying such land would be seen as a sign of aggression and may result in open hostilities). Neutral zones may have been established after a war or other conflict as part of peace negotiations. Fictional neutral zones may contain independent city-states, trading posts, great walls, or watchtowers. They may have different laws and methods of enforcement than the surrounding areas. They may be regions where there is high crime. Travel into and out of neutral zones may be monitored and/or restricted and special documentation may be required. There may be hidden routes into and out of neutral zones and into neighboring regions known only by a few.
When designing neutral zones consider the history that led to their creation as well as the current political relationships between any authority that oversees the neutral zone, and any countries that may wish to claim it.