Town

A town is more defendable and often larger then a city itself. And thus solidifies your position in a region.
Requirements-

16 furnitured houses in your factions theme.

4 larger houses for rich citizens 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.

benefits-

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

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

Disadvantage-

High cost to make.