 In Age of Empires III , the player advances through technological " Ages " , representing historical time periods ; these provide access to greater improvements , units , and buildings . They include the Discovery Age , which represents the discovery and exploration of the Americas by Europeans and allows the player to explore and develop their economy ; the Colonial Age , which represents the European Expansion into the " New World " and unlocks early military units ; the Fortress Age , which represents the fortification of the European colonies , unlocks forts , and allows the player to have a more complete military ; the Industrial Age , which triggers a strong economy , due in part to factories — advanced buildings that automatically produce resources or artillery — and unlocks all units and shipments ; and the Imperial Age , which unlocks all buildings and upgrades , and allows you to send unit and resource shipments a second time . All Ages cost food and coin to advance to , except the Colonial Age , which only costs food ( 800 ) . The price of age advancement is incremental , but does not vary between civilizations . 
