- "The art of war teaches us to rely not on the likelihood of the enemy's not attacking, but rather on the fact that we have made our position unassailable."
- –Sun Tzu
- Enemy land units must expend 1 extra movement per tile inside your territory. The wall encompasses all of the territory of the civilization that has built it.
- Free Walls in the city.
The Great Wall is the earliest defensive Wonder, which can make any potential invaders' life pure hell while trying to penetrate your lands. It's recommended for all players that intend on playing defensively through the game. Just produce lots of ranged units and watch the enemy struggle to approach while they cut their lines down from afar!
Despite being a defensive Wonder, it can be worthwhile to build the Great Wall if you plan to be aggressive in order to deny others and make domination easier. If any enemy manages to build it, they essentially have marshes all along their border, meaning only mounted units (with 3 or more Movement) can reach units two tiles inside the border. This, as mentioned above, shifts the focus of combat towards ranged (and siege) units.
The effect of the Great Wall is negated when the player owning the wonder has researched Dynamite, not the invading civilization. This means the wonder can be of use against even more technologically advanced civilizations, greatly aiding the defense of the owner's lands until late in the Industrial Era.
The Great Wall of China is one of the largest and most famous man-made constructions in the entire world. Chinese rulers built the Great Wall to ward off attack from nomadic tribesmen living in modern Manchuria and Mongolia. Interestingly, the Great Wall was not designed to keep the nomads out - the Chinese knew it was all but impossible to defend such a long border - it was designed to make it difficult for the raiders to carry off loot, thus making raids far less profitable and thus less worth the risks involved.
There have actually been five different "Great Walls" built by different Chinese dynasties. The first four were constructed of earth and have since all but disappeared. The current wall was built almost entirely by the Ming Dynasty between 1368 and 1640 AD. This wall was constructed on a grander scale, using more permanent materials (like stone). The Ming wall stretches for 6,354 km (3,948 miles) from Shanhai Pass on the Bohai Gulf in the east to Lop Nur in the southeast portion of Xinjiang's Uygur Autonomous Region in the west. This was the region where the Silk Road first entered China, and a series of watchtowers which could communicate via smoke signals were intended to pass messages rapidly along the wall's vast length.
In pure military terms, the Great Wall turned out to be something of a failure. While the wall stopped raids, it could not stop an army. The Manchus were able to bribe a Chinese general to let them pass through the wall, so it turned out to be of little value in stopping a major barbarian attack. After the Manchus conquered China, the borders of the country extended far to the north, rendering the wall irrelevant. The sheer monetary cost of the wall was also staggering, and the cost in human lives is said to have exceeded over one million souls. The Great Wall is sometimes nicknamed "the long graveyard."
Today much of the Great Wall is in a state of disrepair - though the tourist regions are well-preserved, much of the rest of the structure is crumbling, and perhaps only 20% of the wall is in good condition. Despite its decay, the Great Wall remains one of China's most popular tourist attractions and a true wonder of the world.
Although the wonder affects all tiles under the owner's control, what you see on the map only extends up to 5 tiles away from the city in which it is built with the exception of coast and ocean tiles, and offshore islands (though the tiles still have to be under your control), and it expands every time you reload the game until it reaches the 5 tile limit in all directions. It can also turn out very ugly, especially if you have any holes in your borders, so the wonder is not really good for any aesthetic-minded players.