Outposts eliminate fog of war. To construct an Outpost, move a worker to any land tile in neutral or owned territory and select the Build Outpost unit action. Construction of the Outpost consumes the worker. The range of vision for the Outpost is 2 tiles on flat terrain, 3 on hills and 4 on mountains. Outposts can only be used by the player who created them. If an Outpost falls within the territory of any other civilization, it will be destroyed. Outposts can only be built in tiles that are empty or have a mine, irrigation, road and/or a railroad. The "Build Outpost" unit-action becomes available after the Masonry advance is researched.