Capital

The capital is essentially a large town where the royalty resides. From here the realm is governed.
Requirements-

24 furnitured houses in your factions theme.

8 larger houses for rich citizens in your factions theme.

2 mansions for the nobles in your factions theme.

1 market with atleast 4 market stalls or shops. (for special events)

2 shops or production sites.

A wall "or" 2 watchtowers "or" 1 castle/stronghold

1 throne room

Benefits-

Unit spawners to solidify your factions presence in that region. Including warrior spawners at defensive structures.

Extra traders for every shop + 8 houses/4 large houses or 2 mansions.

Bonus recources for the production sites.

If the capital gets taken by invading forces, the defenders may countersiege once, right after the battle, unless one of the sides must log off. Then a close date will be discussed, and the capital remains disputed until the counter siege is done.

Disadvantage-

Every nation may have 1 capital only. High cost of establishing a good capital.