The altitude of every land square in the game falls into one of four bands:
- ground level (0–999m)
- medium elevation (1000–1999m)
- high elevation (2000–2999m)
- very high elevation (3000–3500m)
Artillery units receive a +25% attack bonus for each band of altitude that they are above their target.
Adjacent squares can only differ by one band of altitude. Where terraforming or global changes in sea level affect the altitude of a square, neighboring squares will adjust accordingly, which can cause the destruction of terrain improvements.
Note: There is an optional bonus to units attacking from a higher altitude and an optional penalty to attacking from a lower altitude then their target. These bonuses will multiply based on the above altitude bands. These variables are set to 0 in alpha(x).txt. An AI player will not take these bonuses and penalties into account when calculating an attack so they provide a human player with an advantage over an AI opponent.