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.