Cliffs are a type of terrain present in some maps, usually replacing the more common Mountains. Like Mountains, Cliffs provide an impassable barrier for land units. Unlike Mountains however, ranged units can shoot to objectives in the other side of a Cliff, and in fact, units attacking from the higher ground of the Cliff receive an attack bonus against their targets down below.
As is the case with Mountains, Mines can be built on Cliffs, an only one Mine per nation can be built on a Cliff, the size of the Cliff determining how many workers it can sustain, and subsequently, how much Metal can be gathered from it. This makes Cliffs one of the most strategically useful terrains in the game. Rare Resources also tend to appear of the top of Cliffs, making their seizure even more useful.