The majority of buildings are clustered around the daimyo's castle - the whole settlement being known as a "castle town". When you select a castle town or a building elsewhere in a province (such as a port or farm), 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 in the bottom left and the time required is shown in the bottom right of the picture. Buildings facilitate unit production, can increase income and improve governmental control within a province. The number of slots available to build on inside a castle town depends on the level of the castle - so the larger the castle, the greater the number of possible surrounding buildings. Any chain of buildings can be constructed in any of these slots, although some buildings require the presence of certain resources or the mastery of certain arts 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 by use of the dedicated button that appears in the bottom left-hand corner of the screen when a castle town or outside settlement is selected. If simply left, damaged buildings will be automatically repaired very slowly over time at no cost.
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 province to them) by use of the demolish button that appears in the bottom left-hand corner of the screen when a castle town or outside settlement is selected. Castles, ports, roads and province speciality buildings cannot be demolished at their base levels.
The castle is the hub of activity in a province. It is surrounded by the majority of buildings are concentrated - forming the castle town. As such, castles consume the lion's share of food produced, so if farms are not maintained and upgraded there will be food shortages, which in turn could lead to unrest.