 Buildings play a big role in gameplay , as they are used for training civilian and military units , researching improvements , supporting population , providing structural defense or as resource providers . The buildings portrayed in Age of Empires III resemble the architectural design of that era . All of the games in the series share several buildings , including the Town Center and Docks . The appearance and attributes of a building change as the player advances through the Ages , and some civilizations have their own unique buildings . The appearance of these buildings depends on the civilization . Some buildings can only be built at certain times like the defensive towers . 
