Buildings

§ When first constructed, a city is little more than a wide place in the road with several rude huts scattered about. In order for the new city to function effectively, you must construct "buildings" in it. Buildings serve a wide variety of purposes in Civilization IV - walls protect military units during combat, temples make the citizens happier, barracks train troops created in the city, markets increase a city's wealth, and so on. Determining which buildings to construct when - and balancing the need to improve your cities versus the need to create units - will often spell the difference between a successful, prospering civilization and a weak and helpless one.
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How to Produce Buildings

§ City Production Menu: When a city has completed its current production and is ready to build something else, the "City Production Menu" will appear on the screen. This menu displays everything that the city can produce, and may include workers, settlers, military units, buildings, wonders, gold, and so forth. At the top of the menu are displayed two "recommended" items that the game itself thinks you might want to create - but you never have to follow these recommendations. If you are uncertain what to build, highlighting each item with the mouse will display information about what they do. Click on the item you want to produce: construction will begin immediately, and you will be informed when it is complete.
§ On the City Screen: The city screen appears when you double-click on a city on the main map. The city production menu appears at the bottom of this screen (in a different format from the pop-up menu above); double-click on the building you wish to produce. Moving the mouse over the different icons will provide more information about them here as well.
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Building Availability

§ Not all buildings are available for you to construct at the start of the game. Building availability is determined by a number of factors:
§ Tech Requirements: Many buildings have "tech requirements" - that is, you have to have discovered a certain technology before you can build a particular building. For instance, you cannot build a Granary until you have learned the Pottery technology.
§ Location Requirements: Some buildings can be only constructed in cities in certain locations. These are usually fairly obvious: harbors, for example, may be built only in coastal cities.
§ Previous Construction Requirements: Certain buildings cannot be built in a city unless other buildings have been constructed first. A city must contain a market and a grocery before you can build a bank there.
§ Religious Requirements: Some buildings have religious prerequisites. For example, you cannot build a temple in a city until that city has acquired religion.
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Time to Produce

§ The time to produce a building is dependent upon the city's production output (see Cities for more details) and the production cost of the building itself. For instance, if a city with a production output of 20 begins work on a building with a production cost of 100, it will take that city 5 turns to complete the building.
§ Other factors may speed the time of production. Some civilizations get bonuses when constructing certain buildings. And access to specific resources - copper, stone, marble - may speed production on certain buildings; for example, the Pyramids can be built much faster with the stone resource. Further, certain Civics affect building production times.
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Maintenance Costs

§ Unlike previous Civilization games, there are no maintenance costs associated with buildings in Civilization IV. Maintenance costs are attached instead to cities.
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Capturing Buildings

§ When you capture a city, some of its buildings may be destroyed, but others may remain intact for your use. Captured buildings function just like other buildings.