Buildings are unlocked after researching particular technology (except the Monument, which is unlocked from the start of the game). They may be built in a city via the normal production process, or bought instantly with currency ( Gold or Faith). To do this, go to the city screen, and look to the left - there you'll see a list of all buildings available to build or purchase. Click on the "Change Production" button bellow to assign a new construction project for the city, or on the "Purchase" button to instantly buy a building with some currency.
Many times building construction is subject to prerequisites - in this case, the building may not be built or bought in this city until you meet the prerequisites. It will appear in the list, but will be grayed out.
The following types of prerequisites determine whether or not you can construct a building in a particular city:
- Other buildings - Many of the buildings in the game are organised in "chains," or "trees" - those that are further up the chain, or tree, will require the ones preceding them.
- Terrain features - Some buildings require the city tile (the one on which the city is placed) or a nearby tile to contain a particular type of terrain or feature, such as flat terrain or hills. Some buildings require the city tile to border a river or the coast. Others require the presence of a mountain within 1 or 2 tiles of the city.
- Resources - For this requirement, certain Resources must be controlled by the city (i.e. this city must be working them). A Forge, for example, may be built only if there is Iron nearby. Most of the time, the requirement also includes the resources in question to be improved (have the necessary improvement in working condition, but not necessarily worked by a Citizen).
Almost all buildings cost some Gold per turn as maintenance. You can also sell buildings - go to the city screen, then find the building you want to sell in the list to the right, and click on it, then confirm. For more information on selling buildings, see below.
Certain buildings are called World Wonders. Those are unique mega-buildings, representing real-world-famous buildings, for the purposes of the game. They cost much more Production points to be built, and cannot be purchased with currency. What's more, they can only be built once in the whole world! That means that if another civilization manages to build a Wonder before you, neither you nor anyone else may build it anymore.
World Wonders may have terrain prerequisites, too. They don't depend on Resources or the presence of other buildings, though. In Brave New World, many Wonders may only be constructed once a player unlocks certain Social Policy tree or adopts a certain Ideology.
The presence of improved Marble resource controlled by the city gives it a 15% bonus when constructing Wonders, but only in the Ancient and Classical Eras.
There's also a second type of Wonders: the National Wonders, which are unique to each civilization (i.e. no civilization may have more than one of each National Wonder). Most National Wonders require a certain normal building to be present in all cities you control directly (non-Puppet cities), although there are a few that are exceptions to this rule.
Like World Wonders, National Wonders can't be purchased with Gold. In addition, their Production cost goes up the more cities there are in your empire, so try to build them before you expand too much.
You may sell any building you have in a city, excluding Wonders, any "business" buildings (those from the Gold production chain, such as the Market), any defensive buildings (Walls, Castles, Arsenals, Military Bases, and their replacements), and any buildings which cost no maintenance. You also can't sell Great Work buildings whose slots are currently filled - you must move the Great Works first.
You will receive a small amount of Gold for selling a building and will no longer have to pay its maintenance fee, so your cash flow may change. Of course, you won't be able to use the building's benefits anymore, so it is not advisable to sell too many buildings unless your budget is in dire straits indeed.
In order to prevent you from selling all of the buildings in a city that is about to be captured by an enemy, the game allows you to sell only one building per city per turn.
When a city is conquered during war, a number of its buildings get destroyed. First, all defensive buildings are leveled by the siege, but a number of other buildings (usually early ones, like a Monument) get destroyed as well. Of course, this doesn't matter much if the conqueror sets the city on fire!
Tile improvements (often called "improvements" for short) are vaguely similar to buildings, but are specifically oriented towards terrain improvement and can only be built on the tiles surrounding a city. They are also vital for your empire's development because they allow you to access the full potential of the land you control. Tile improvements are constructed by Workers (in which case they take several turns to finish), or by Great People (in which case they're called Great Person tile improvements and are built instantaneously). Tile improvements on sea resources are constructed instantaneously by Work Boats. Roads, Railroads, and Forts may be built anywhere, but other improvements can only be constructed on tiles which are inside your territory.
Improvements' primary function is to improve the potential output of the tile they're built on. However, keep in mind that they still need to be worked by Citizens to contribute their potential to the nearest city. Their secondary, and often even more important function, is to access the special abilities of Strategic and Luxury Resources. These abilities become available even if the tile isn't worked by a Citizen, although you won't enjoy the bonus tile yields all these resources offer.
Improvements, like buildings, cost Gold to maintain.
Unlike city buildings, improvements are vulnerable out in the open. Enemy armies may pillage them, which will render the improvements inoperable until repaired by a Worker. Pillaging an improvement heals the pillaging unit for 25 HP and nets their civilization some Gold.
For a list of improvements, go here.
Buildings are an essential part of the game. They enhance greatly the productivity of your cities in all aspects of the game. As a general rule, when you're not constructing a unit in a city, you should be constructing some building. Which one, exactly, depends on three things:
- What is the current situation of your empire? If you're dangerously short on something (money, military power, workers, etc.), you should focus on remedying the situation via certain constructions in every city.
- What is the current situation in a particular city? If it is lacking food, production capacity, or something else, try to construct a building that provides what it needs.
- What are your overall game goals and strategies?
Following this order of importance, you should decide what to build in your cities. This way your empire will progress nicely and with a purpose.
Keep in mind that many buildings' bonuses consist in percentage over some base. This means that the building, when constructed, won't directly add to the stat in question, it will simply increase its base value for that city by the given percentage. In practice, this means that such buildings are more effective in cities which already produce a considerable base number of this stat. For example:
- We have City A and City B. City A produces 20 Gold per turn, while City B only produces 6 Gold per turn. We want, then, to construct a building that enhances Gold production by 50%. What would the result be in each city?
- In City A, we will get 20 + 10 (which is 50% of 20) = 30. In other words, the net increase is 10.
- In City B, we have 6 + 3 = 9. The net increase is just 3.
- So, we'll get a much better immediate result if we construct the building in City A. In City B, we'll also get a result, but by far not as expressive. While we may want to eventually construct the building in City B, we should make other priorities there, since this building won't generate that much overall benefit for the empire.
The thing to remember here is that it's always better to construct buildings with percentage-based bonuses first in the cities that will benefit from them most (i.e. the ones that have the biggest base production of the type). You can later construct them in the other cities, too, but in the meantime, you'll have enjoyed a large boost of the stat in question for a relatively short time. Of course, this rule is always subject to more immediate concerns.
Building tile improvements is essential for your development, especially when they give access to Luxuries or Strategic resources. However, keep in mind that each improvement costs Gold, and is only useful if its tile is worked by the nearby city. So, sometimes it's not worth it to cover all land near the city in Farms, only to get some more Food, and when most of the tiles won't be worked anyway because your citizens have more important tasks. So, don't be so quick to built Improvements on tiles that don't contain resources - only do this when your city grows and you will have enough citizens to work around the city.
Now, building a Road network is always useful - connect your cities by Roads as early as possible both to establish City Connections and to ensure quicker movement for your units. Later in the game upgrade the Roads to Railroads, also ASAP - they're really useful as well. Forts, on the other hand, are a waste of space and Gold most of the time - only construct them if you really need them, for example when under imminent threat from an invasion.
Finally, concerning World Wonders: without question they are of great importance to the game, but they come with a catch. Every Wonder costs considerable amount of PP, and while constructing it, your city won't be able to construct anything with more immediate benefits. Keeping in mind that Wonder construction is actually a race between all players in the game; you need to carefully plan when and where you're going to attempt to construct a Wonder, and then concentrate your efforts. Research the necessary technology ASAP (leapfrog earlier technologies, if necessary!), then start the construction immediately. Boost it by manually assigning citizens to maximize Production or by cutting nearby forests, so that you have a better chance of completing the Wonder before other civilizations. The gold that you'll get as a consolation prize if another civilization completes the Wonder first is certainly nice, but it's usually far from the benefits a completed Wonder gives your civilization. Plus, you'll have wasted a number of turns that you could have spent building something else useful.