When you select a settlement, the construction tab will appear. Left-click on a building to add it to the construction queue, and again to remove it. The cost of construction is displayed at the bottom and the time required is shown in the top left of the picture. Buildings facilitate unit production, can increase income, and improve governmental control within a province. The building chains constructible at each settlement often depend on the availability of particular resources, or the research of certain technologies, before they can be constructed. Right-click on a building's picture to view its description and statistics.
Buildings damaged during sieges or through sabotage can be repaired. If simply left, damaged buildings will be automatically repaired very slowly over time at no cost. However, if a building is ruined you must select it and click on the repair button that appears when you mouse over the building on the settlement panel.
Buildings can be demolished if you want to construct something else in their place (or leave nothing of value to an invader if you are about to lose a region to them) by use of the demolish button that appears when you mouse over a building on the settlement panel. Settlements and ports cannot be demolished at their base levels.
When your faction reaches the top of a building chain and a certain event has occurred it may then be possible to construct a legendary building. If you are the first to construct one your faction will be awarded a permanent faction trait and its associated effects. Guard your legendary buildings well, they will quickly become a target for your enemies.