In addition to Buildings, Civilization IV also contains Wonders, which are unique structures that have high production costs, but provide additional gold, culture, or other potent benefits when completed.
While National Wonders are restricted to one per civilization, Great/World Wonders are restricted to one per game. In addition, there are also Projects, which have effects similar to Wonders.
Projects adhere to the same construction rules as Wonders except that they cannot be hurried.
All Projects are unlocked by modern-era technologies, with the exception of The Manhattan Project, which is unlocked by Fission, an industrial-era technology.
World Projects[]
Just like World Wonders, they can only be built once per game.