The Tigris river winds through the cradle of civilization, providing food, water, and a means of transportation for trade and dissemination of ideas between the various cities and towns along the way.
In Trade on the Tigris, you are one of these cities. Each round, you gain development cards that provide new abilities, produce resources (in the form of cards), trade them with the other players, and turn in sets of these for profit (points). An inevitable side effect of this interaction with others is the sharing of philosophies. The primary religion and government of your city may be shaken to its very core as a result, and the ways in which you can develop the abilities of your city will change along with them. After 5 rounds, the player with the most points, wins!