The Academy is one of the buildings in a city. It is used to unlock new technologies like new soldiers, or improve units the player has already unlocked. Production of resources can also be improved by upgrading.
For each level, players must have a City Hall of the same level first. To build a level 1 Academy, it is also mandatory to have one Dwellings Lv1. Construction time varies between players, depending on their Political Points and other factors.