Trade in Civilization Revolution is tied to gold and science production. Trade can be either gold or science depending on what mode a city is placed in. It appears as an icon on the map in sea and desert squares as a circle with two arrows curved toward each other. Trade is affected by a civilization's abilities, form of governmentwonders, and buildings. It is also affected by certain technology upgrades, such as CurrencyWine is the only resource which provides trade rather than gold, science, or culture.