Also a
card game for two players. The card game is based on the
board game, with many of the same concepts (like the
resources,
roads,
cities, etc.), but abstracted away from the
map used in the board game. A lot of special cards are added, giving more variation (e.g.
industries adding resources,
commerce buildings,
knights and many more).
Personally, I still prefer playing the board game, but the card game is a good substitute if not more than two players are available. It is one of the few good games that work well with two players.