The Wonders of the World are unique, extraordinary achievements, which bring continued rewards to the possessors. Some are structures (the Pyramids) and some are abstractions (Women's Suffrage), but all are modeled in the game as "buildings" that are erected in a particular city.
A Wonder is "constructed" like any other city production, at a cost in production points. There is no limit on the number of cities in the world (indeed, in your own civilization) that may be working on the same Wonder, but only one city will complete it, based on when its production finishes in the turn update. All cities other than the one to complete it will be forced to redirect their production to other projects.
While a Wonder is being constructed in a city, Caravan and Freight units have a new ability. When such a unit enters a city where a Wonder is under construction, the unit is able to add its production cost (50 production points) to the Wonder, at the expense of the unit. It is a common strategy to have cities build such units, to stockpile them until an advancement is discovered allowing a certain Wonder, and then building the Wonder in as little as one turn by consuming the Caravans.
Almost all Wonders give benefits only to the civilization that possesses them (exceptions: Manhattan Project, Apollo project). Some Wonders aid just the city in which they stand; others influence the entire empire.
When a city containing a Wonder is captured by a rival civilization, the Wonder becomes the property of the new owners of the city, and they immediately benefit from it. Those benefits accrue to the new owner even if that civilization lacks the required advance to build it.
Wonders of the World can become obsolete, in much the same manner as buildings and units. However, unlike units, they cannot be upgraded. Once the technology that obsoletes a Wonder is discovered by any race, the Wonder ceases to exert its beneficial effect, though it does add three gold to the national treasury per turn. Wonders may not be sold. They do contribute to the empire's score at the end of the game.
This table shows the Wonders of the World, the civilization advancement required to build each, the production cost, and the effect. For some, there is a "variant" effect, activated if the variant field for the Wonder is set in the ruleset file.
Adam Smith's Trading Co | Economics | 400 | For the entire empire, city buildings which would normally have an upkeep of one gold are free. |
Apollo Program | Space Flight | 600 | All cities in the world become visible to the Wonder's owner, in every turn. Permits construction of spaceship elements for all nations with the required technology. |
Colossus | Bronze Working | 200 | Each square within the area of influence of the city in which this Wonder is built produces one extra trade point. Made obsolete by Flight. |
Copernicus' Observatory | Astronomy | 300 | Boosts research production in its city by 50%. No other education buildings are required for this benefit. |
Cure For Cancer | Genetic Engineering | 600 | Makes one unhappy citizen content in all the cities of the owning empire. |
Darwin's Voyage | Railroad | 300 | Gives the builder two immediate free advances. |
Great Library | Literacy | 200 | The civilization owning this Wonder automatically receives every advancement that at least two other civilizations have discovered. Made obsolete by Electricity. |
Great Wall | Masonry | 300 | Serves as a City Wall in each of the owning empire's cities. Made obsolete by Metallurgy. |
Hanging Gardens | Pottery | 200 | Makes one unhappy citizen happy in every city of the empire; in the city with the Wonder, makes a total of three unhappy citizens happy. Made obsolete by Railroad. |
Hoover Dam | Electronics | 600 | Can only be built in a city on or next to a Mountain of River square. Benefits the owning empire as if every city in the empire had a Hydro Plant. The variant form of Hoover Dam only has effect across the continent in which it is built. |
Isaac Newton's College | Theory of Gravity | 400 | Boosts research production in the city of the Wonder by 100%. Does not require any other educational buildings for this benefit. |
J.S. Bach's Cathedral | Theology | 400 | Makes two unhappy citizens content in every city of the owning empire. The variant form only has effect across the continent in which it is built. |
King Richard's Crusade | Engineering | 300 | Adds one production point to every square in the area of influence of the city containing the Wonder. Made obsolete by Industrialization. |
Leonardo's Workshop | Invention | 400 | Every turn that this Wonder exists, and the owning nation has at least one obsolete unit, the Wonder will upgrade one unit for free. Made obsolete by Automobile. |
Lighthouse | Map Making | 200 | Gives all sea units of the empire one additional movement point, and eliminates the risk of that empire losing Triremes at sea. All sea units built in the city of the Wonder are automatically veterans. Made obsolete by Magnetism. |
Magellan's Expedition | Navigation | 400 | Gives all of the owner's sea units two additional movement points. |
Manhattan Project | Nuclear Fission | 600 | Allows all players in the game with knowledge of Rocketry to build Nuclear. |
Michaelangelo's Chapel | Monotheism | 400 | Every city in the empire acts as if it had a Cathedral, with the same adjustments due to Theology and Communism. |
Oracle | Mysticism | 300 | Doubles the effect of Temples in all cities of the empire. Made obsolete by Theology. |
Pyramids | Masonry | 200 | Every city in the empire acts as if it had a Granary. The variant form of Pyramids allows you to choose any government type without the transition period of Anarchy. |
SETI Program | Computers | 600 | Every city in the empire acts as if it had a Research Lab (if it has a Library, but performs its function even if there is no University). |
Shakespeare's Theatre | Medicine | 300 | Makes all unhappy citizens content in the city of the Wonder. |
Statue of Liberty | Democracy | 400 | Allows the owning civilization to change to any government type, even if the advancement for that type has not been learned, and also changes the government type without the transition period of Anarchy. |
Sun Tzu's War Academy | Feudalism | 300 | Every city in the empire acts as if it had a Barracks (I, II, or III). Every land unit of the nation that survives a combat becomes a veteran. Made obsolete by Mobile Warfare. |
United Nations | Communism | 600 | Units of the owning empire regain one more hit point per turn than otherwise. The variant form allows you to choose any government type without the transition period of Anarchy. |
Women's Suffrage | Industrialization | 600 | Every city in the owning nation acts as if it had a Police Station. The variant form of Women's Suffrage reduces by one the unhappiness effect of every military unit (not just one unit per city). This means that in a Republic, units do not cause unhappiness, and in a Democracy, aggressive units cause only one unhappy citizen each. |