Wonders are the remarkable, one-of-a-kind buildings that ensure that a civilization will be remembered throughout all of history. Wonders engage the mind and lift the spirits.
The Pyramids, Notre Dame Cathedral, and Stonehenge are examples of wonders. Wonders require much time and energy from your cities to construct, but once completed, they provide your civilization with many benefits.
There are three basic types of wonders: World Wonders, National Wonders and Project Wonders. Only one copy of a World Wonder may be constructed anywhere in the world in a given game. National Wonders are less exclusive: each nation may construct one (but only one) copy of a National Wonder.