In Rise of Nations, Forest is a prominent terrain, being the main source of Timber, one of the first and most important Basic Resources. A considerable gather rate of Timber can only be attained through a Forest with a Woodcutter's Camp built on it. The more trees surrounding a Woodcutter's Camp, the higher Citizen capacity the camp will have, and the higher its maximum gather rate of Timber will be. Unlike Mountains or Cliffs, which only allow one given Mine per nation to be built to gather Metal on them, a Forest has no limit on the amount of Woodcutter Camps a nation can build on it. However, a new camp with an overlapping area of workable trees will not be able to gather from them if the trees are already being worked by another camp, hence multiple camps in the same Forest will only be truly useful if the Forest is large enough for the addtional camps to have enough trees for themselves alone.
Forests are also impassable barriers to all land units, except by the Iroquois Scouts. This means that Forests can create choke points and narrow passages of great strategic value. This holds specially true in maps with large, dense Forests, such as the Amazon Rainforest. This effect is even stronger if Forests are accompanied by Mountains or Cliffs, which are also impassable for land units, without exception.
Some maps of a more "arid" nature, such as African Watering Hole, may contain almost no Forests, only individual trees and small, scattered patches, making the efficient production of Timber both a bigger problem and a higher priority for the players.