The most vital buildings in the game; and the other kind of buildings.
Building that is the heart of your town. Upgrades affect entire city. If all of your Town Center is destroyed, then: 1. on the story plot - you lose. 2. On multiplayer, you have a limited amount of time to [re]build a Town Center or you lose.
In the Campaign, it's just something to look at. In Multiplayer, when you build one of these, you just have to protect the water during the countdown to win. This is the Passive way to win in Multiplayer.
Gate used to summon a Titan. More info about this building under Titan.
A building that can Transport a set amount of units to any other Sky Passage. (Garrisoned)