The map has some holes, representing impassable provinces. Routes into some provinces may also be hidden.
Plain [cd21], plain, in region Tollus Routes leaving Plain [cd21]: North, to Plain [cc21], 7 days East, to Plain [cd22], 7 days West, to Plain [cd20], 7 days
Notice the lack of a southern exit. This means that there is no known southern route from Plain [cd21], into what should be Plain [ce21]. Exploration may find a southern route, but it is possible that none may ever be found, and the terrain to the south is completely impassable.