Trade is a key to a successful Civilization by dramatically increasing its income of <l:6,92>gold<e>. The goal of trade is to collect as many of the same <l:6,94>goods<e> as possible in a single city, thus creating a very valuable monopoly. The greater the monopoly, the more gold the city earns. In the trade system, a ruler can do one of three primary actions: send a good from one of his cities to another by employing a <l:1,155>Caravan<e>; he can also buy and sell goods with foreign Civilizations. A ruler must be wary of <l:6,23>piracy<e>. A ruler can access trade through the trade advisor.