National Wonder. Can only be built once in your empire. To unlock: Requires that you are at War with other Civilizations. Must be built adjacent to an Encampment district.

+1 Military policy slot. Provides the same defensive bonuses as the Fort improvement. Grant Walls and Medieval Walls in this City. Promoting a unit does not end that unit's turn. +4 Combat Strength for all military units in your territory. All buildings in Encampment districts provide +2 Production and +2 Culture. +100% Encampment district Production adjacency bonuses. Military Engineers gets +1 Movement and +1 build charge.

+2 Tourism
+1 extra per Era that you've advanced past this Wonder's era

故用兵之法，无恃其不来，恃吾有以待也；无恃其不攻，恃吾有所不可攻也。
——《孙子兵法》