This patch changes the vision range of wall segments, palisades, Iberian monument, Mauryan pillar, and Roman arch to 1. This means you can select them, but they won't reveal their surrounding area. They're basically pieces of stone, wood, and metal, so it's unnatural to have them see things. (For comparison, field has 0.) Ranged infantry on walls still has an extensive range, of course.
- Wall towers are garrisonable and have a ranged attack, which means they need to have a vision range larger than their maximum attack range, hence changed from 60 to 80.