Each Territory has three states:
Most diplomatic Grievances only apply on Territories claimed by Cities. If an Empire does not allow another to cross their borders, it will only apply to borders of Territories claimed by or attached to Cities.
A City can attach an Outpost if they’re adjacent by paying a certain amount of Influence . The cost is based on the number of Outposts already attached to the City.
When an Outpost becomes attached to a City, the City benefits from the attached Territory’s exploitations, but it is no longer possible to queue constructions in the Territory: The Construction Queues from the City and Outpost are merged together.
Once an Outpost becomes attached to a City, players can detach it for free, but you’ll need to pay the attach cost again if you want to re-attach it.
The same process can be done with two Cities. In that case you choose which City to merge with another adjacent one. There will be an Influence cost, similar to the one for the Attachments.
In order to merge two Cities, you have to unlock a special ability that is gained by researching the proper Technology.
Each Territory has an Administrative Center. It is a status that only one Tile per Territory can have.
When an Empire makes a trade by buying a Resource, a link is created between the Resource Deposit and their closest City. The link will obligatorily cross the Administrative Center of all the neutral Territories it goes through. A Trading Post will be created on all Administrative Centers crossed that way.
A Trading Post is a District that other Empires can ransack to gain Money, breaking the Trade Route in the process.
If an Empire places an Outpost or a City on a Territory, the Administrative Center status is transferred to that Tile.
If the Administrative Center of a Territory you own falls, the whole Territory’s ownership falls with it.
If an Administrative Center is destroyed by a Bombardment or Ransacking, then its whole Territory will become neutral, all Districts will become uninhabited and all trade moving across it will be halted permanently. Your Empire will need to claim it again to recover your exploitations, and most Districts will need to be repaired in order to function again.