Border growth expands the territory of a city by one tile in all directions (from a 3x3 area to a 5x5 area) into neutral tiles only. It also explores all unexplored tiles within a two-tile radius of the city. Border growth is one of the rewards for upgrading a city to level four, the other being population growth. Note that every tile in the player's territory is worth 20 points (so border growth increases score by up to 320 points) and every explored tile is worth five points.

Notice how the city does not expand into other cites' territories

City Upgrades
Workshop Explorer | City Wall Resources | Border Growth Population Growth | Park Super Unit
Community content is available under CC-BY-SA unless otherwise noted.