Unique buildings are vital to your city, and either start prebuilt, or require to be repaired as your city grows.
Citadel is the centerpiece structure of your city. Much of what you can do is determined by the level of your Citadel. Upgrading the Citadel unlocks additional building slots, construct and upgrade buildings, statues, and ultimately access various parts of the game.
Starting at level 10, your Citadel will receive a durability rating. Losing defensive battles in your city — on the Wall — will set your Citadel on fire, dealing damage. Fires can be put out ahead of time, and the Citadel has to be repaired afterwards. If your city burns down, you will receive hefty penalties to your construction and research, as well as in other areas.
You can find various useful information on your city in your Citadel, such as city resources, structures, boosts and more.
Requirements: Wall, House, Barracks, and an extra building (varies by level)
The Wall is the main defensive structure of your city, providing you with the means to deploy armies and protect your Citadel. If an enemy attacks your city, they will have to defeat the army deployed to the Wall to plunder your city. If they're victorious, you will lose a share of your unprotected resources and your medals, your Citadel will be set on fire. If you allow it to burn, you may end up with a razed city that will impose negative penalties on construction, research and other stats, and may take a while to repair.
Upgrading the Wall increases the capacity (weight) of the army you can deploy. This capacity can also be temporarily increased by building a Statue of Defense.
Tapping on the Wall allows you to deploy an Army, use related consumables (flasks, shields, etc) and more.
You can receive additional rewards for keeping your Wall manned at all times without losing defensive battles in your city. Tap on "Prize List" to find out more.
Requirements: Barracks, House
The Port allows you to fulfill trade orders by loading and sending away trade ships in return for alliance credits, stardust, port points and tablets. The Port starts destroyed on the eastern shore of your city, and can be repaired once you reach Citadel level 10.
Upgrading the Port increases the rewards provided when sending ships. Additionally, in order to upgrade the Port, you will need to obtain Anchors available in the regular store, alliance store, rewards in events and tournaments, and in some special offers. The Port can only be upgraded to level 10.
Altar of Summoning
The Altar of Summoning allows you to summon and pray to Lesser and Elder Gods in the game. Lesser Gods are available in every alliance at the start, while Elder Gods have to be researched in the Alliance Temple tab.
Praying to Gods grants alliance credits, alliance points and a production boost to specific resources depending on the god summoned.
The Altar also allows you to synthesize tablets from lower to higher tiers using stardust.
Upgrading the Altar reduces the time required to summon a god, while the level 2 Altar allows you to summon Elder Gods.
Watchtower provides your city with an area of influence, that primarily allows you to interact with global map objects (outposts and bastions, for example) without having to march to them, if they're within your area of influence. If two cities find themselves within one another's area of influence, the one with lower Power rating will be forced to teleport away.
If your city is located within the borders of your alliance, your Watchtower contributes its points of influence to the total alliance area of influence.
Upgrading the Watchtower increases the amount of influence points provided, which can be further increased with Alliance Patron subscriptions, certain city skins and so on. Additionally, upgrading the Watchtower requires Lanterns that can be obtained in the store, events, quest rewards and more.
Requirements: Wall, Barracks, House