From Civilization V Wiki
Great People are the artists, merchants, engineers, scientists and warriors who can, singlehandedly, change the course of a civilization. They're people like Leonardo Da Vinci, Andrew Carnegie, Louis Pasteur, and Robert E. Lee. Great People are extremely powerful. Great People are cool.
There are five types of Great People: Great Artists, Great Engineers, Great Merchants, Great Scientists, and Great Generals. The first four types are quite similar in functionality, while Great Generals are rather different: they are generated differently and they have different effects upon play. Great Generals will be discussed in detail below; first, let's examine the other four types of Great People.
Generating Great People
Great Artists, Engineers, Merchants and Scientists are created in cities by specialists and Wonders which generate "Great People" (GP) points. A city may generate no Great People points, or it may generate a single kind of GP points or it may generate multiple kinds of GP points. Each city's GP points are kept track of separately. (For example, Kyoto might generate 1 Artist and 2 Engineer GP pts each turn. After 3 turns it would have 3 Artist points and 6 Engineer GP pts. The two types of points are not pooled.)
When a city has enough of a specific type of GP points, the points are expended to generate a Great Person of that type. Once a Great Person is generated, the amount required for the next Great Person increases in all of that player's cities.
For instance, let's say that a player needs to acquire 10 GP pts to get a Great Person. From the previous example, in five turns Kyoto would have enough Engineer GP pts. to create a Great Engineer. After the Great Engineer was created, Kyoto would have 0 Great Engineer points and 5 Great Artist points left, and the amount required for the next Great Person would increase to say 15 points. Eight turns later Kyoto would have 13 Great Artist points and 16 Great Engineer points, and it would generate another Great Engineer. Note that a Garden building increases the rate at which you generate Great People, and that the "Warrior Code" social policy immediately generates a Great General.
Each Great Person type has three abilities (but see the Great General, below).
- They can be expended to create a golden age.
- They can be expended to construct a Special Improvement.
- They have some other special ability.
Note that the names of the Great People have no effect upon play. Beethoven and da Vinci are both Great Artists and both have the same powers.
A "Golden Age" is a period of special productivity for a civilization. During a Golden Age, any tile which produces gold produces 1 extra gold, and any tile which produces production (hammers) produces 1 extra hammer. (Obviously this has no effect unless citizens are working the tiles.) The duration of the Golden Age depends upon the game difficulty and speed. The Great Person is expended when he or she creates a Golden Age.
Each Great Person type can be expended to create a Special Improvement on a tile within your civilization's borders. The Special Improvement's effects depend upon which Great Person is creating it – a Great Artist's Special Improvement generates culture, for example, while a Great Merchant's generates cash. A Special Improvement must be worked in order to have any effect. A Special Improvement can be pillaged and repaired like any other Improvement. If constructed atop a resource, the Special Improvement will not provide access to that resource. Note that you have to move the Great Person out of the city and into your territory to construct a Special Improvement. See below for details.
The Great Person's Special Ability can have major effects upon the game. Once again, each Great Person type has a different Special Ability. Some (but not all) Special Abilities require you to expend the Great Person.
Moving Great People
Great People can move about the board like any other units. They are non-combat units, which means that they cannot stack in a tile with other non-combat units (Workers, Settlers), but they can stack with one military unit. If an enemy unit enters a Great Person's tile, that Great Person is automatically destroyed (the enemy doesn't get it.)