Scoring
Throughout the game, if a player scores so as to finish with exactly a certain number of points, they may take special "wall tiles", which allow players certain actions. Wall tiles, for the most part, allow for certain scoring bonuses at the end of the game. Certain wall tiles allow for extra turns, while others can be used to double the scoring of a particular completed feature.
The game ends whenever all tiles have either been placed or are out of play. At this point there are at least 16 vacant spaces on the board. The player with the largest keep (which may vary due to wall tiles which increase the value) increases their score by the largest number of contiguous empty spaces on the board. Followers on incomplete features (i.e. roads, houses, and towers which border a vacant space) are removed, or scored for reduced value if the player has the appropriate wall tiles.
Finally, fields are scored. Fields score three points for each market (a feature found on certain tiles) on the field (subject to normal scoring rules).
The player with the greater amount of points is declared the winner.
Read more about this topic: Carcassonne: The Castle