Being an immensely popular game, Carcassonne has received a number of expansions. These expansions require the original Carcassonne to play, and they can all be combined together in any configuration. It's daunting to teach somebody to play with all of the expansions, but the new rules are easy to pick up when each expansion is introduced individually. The expansions to Carcassonne are:
The 12 river tiles replace Carcassonne's solitary starting tile. The rules say that the original starting tile isn't to be used, but the game is perfectly playable with the tile included. The river is assembled by the players in the first 12 turns, and followers may be placed as normal at this time. There are two types of river tiles, straight and turn. The river can not turn the same way two turns in a row even if the placement would otherwise be legal. This avoids sharp U-turns in the river. An updated version of this expansion, called "The River II" is also available. The tiles differ slightly and mesh better with the other expansions, but its purpose is the same as the original "The River" expansion. I like to play with both river expansions (only use one of each end point and you have a 22-tile long river).
Inns & Cathedrals:
"With risk comes reward" is the theme of this expansion. Cathedral tiles are four-sided city tiles that triple the point value of a city. If an unfinished city contains a cathedral, however, it is worth zero points. Inns work much the same way in that they double the point value of a completed road, but any incomplete road with an inn is worth nothing.
This expansion also includes a sixth set of followers and one large follower for each player. The large follower is worth twice as much as the small followers -- adding another strategic element to the game. Scoring tiles are also included to account for the score card's limit of 50 points.
Traders & Builders:
More points for everyone! This expansion provides each player with two special followers, the builder and the pig. The builder is placed in a city with at least one follower. When the builder's city or any road leading from it is expanded, the player may draw another tile. The pig increases the value of any one farm by 50%.
The landscape tiles in this expansion have resources printed on them. The resources one can collect are wine, grain, and cloth. The player who completes a city collects the resources from it even if he receives no points for it. Whoever has the most of each resource type receives bonus points at the end of the game. A cloth bag for holding the landscape tiles is also included in this expansion.
King & Scout:
King & Scout, although a single purchase, is two expansions for two separate games. Seven of the 12 tiles are for Carcassonne, and the other five are for Carcassonne: Hunters and Gatherers. Two of the new tiles are special, non-playable tiles. The King tile is held by the player who has completed the largest city in the game, and the Robber is held by the player who has completed the longest road. Size is measured in tiles, not points, so the points modifiers from the "Inns & Cathedrals" expansion don't create any difficulty. At the end of the game, the player holding the King receives one extra point per completed city, and the player holding the Robber receives one extra point per completed road.
The Count of Carcassonne:
This expansion brings the city of Carcassonne to the center of your tile-laying game empire. Twelve tiles represent the city of Carcassonne, and the action begins there. If the "The River" or "The River II" expansion is also being used, the river is connected to Carcassonne, and play continues from there.
Carcassonne is broken up into four districts: the castle district, the cathedral district, the market district, and the blacksmith district, and the Count begins the game in the castle district. Each time a player lays a tile that results in an opponent gaining points, he can move a follower (even the large follower from the Inns & Cathedrals expansion) into one of Carcassonne's four districts. He may also move the Count to another district, but this is optional. When a scoring opportunity is completed (city, road, cloister, or farm), a player with a follower in Carcassonne may move any or all of his followers from the appropriate district of the city to the scoring opportunity. Followers may be moved from the castle district to a scoring city, from the blacksmith district to a scoring road, from the cathedral district to a scoring cloister, and from the market district to a scoring farm. No followers can be moved from the Count's current district.
Princess & Dragon:
The city of Carcassonne is set upon by a dragon intent on wreaking havoc and keeping you from scoring points. Two new figures come with this expansion -- a dragon and a fairy. There are four types of new landscape tiles: volcanoes, dragon movement tiles, magic gates, and castle ladies.
Volcano tiles are home to the dragon. When the first volcano tile is drawn, it is played as normal and the dragon is placed on it. No follower may be placed on a volcano tile (apparently the people of Carcassonne aren't big ash farmers). Dragon movement tiles are just like normal landscape tiles except that they have a picture of a dragon on them. When a dragon movement tile is drawn the player may place a follower as normal. Then, starting with the current player, each player moves the dragon six tiles in one direction, or to a dead-end or the fairy, whichever comes first. Any followers encountered by the dragon are returned to their owner and no points are scored. If a dragon movement tile is drawn before the dragon is out, it is reshuffled and a new tile is drawn (I don't even put them in the sack until a volcano is out).
On any turn, the player can move the fairy to a tile with one of his followers if he chooses not to (or can not) place an additional follower. The player gains one point for each turn that the fairy shares a tile with his follower (this motivates players to move the fairy). Also, the dragon cannot enter the same tile as the fairy, so it provides defense for your followers.
Magic gate tiles bend the rules of follower placement. When a magic gate is drawn, a follower can be placed on any tile. Normal rules still apply, but one could claim an open city or road or strengthen his hold on an existing city or road.
Castle ladies are useful for taking over cities. When a castle lady is played, the player chooses one follower and returns it to its owner. Watch out, this applies to the current player as well, so don't play castle ladies on your own cities!
A cloister in the city can be played as a normal cloister would be, and a tunnel connects the two roads, but not the two farms.
The original Carcassonne is a wonderful game, but its longevity is greatly improved with these expansions. Each is affordable, and there is no need to play with all of the expansions all the time (I do, but that's just because I don't keep the tiles separated). The cheapest I've purchased ("King & Scout") cost $4.00 USD and the most expensive ("Princess & Dragon") cost $15.00 USD. Each bring something new to the table, and fans of the original game shouldn't miss these enhancements to the game!