COMMUNISM
A government of the scientific state. Every city produces HALF AGAIN as much SCIENCE.
It earns no trade bonus from roads, rivers or ocean — the republics out-earn it — but it turns what commerce it has into research far more efficiently.
Distance from the capital NO LONGER matters: corruption is charged as though every city sat ten tiles out, so the furthest province is as governable as the nearest. A PALACE halves it again.
MARTIAL LAW: each military unit garrisoned in a city keeps one citizen content, up to three.
Its people feel no unhappiness over armies abroad, and sustained disorder will not topple the state — where a republic or a democracy would collapse into ANARCHY.
The government of a very large empire that intends to out-think its rivals rather than out-trade them.
REVOLUTION: a town of eight or fewer, three turns in riot, may join a Communist neighbour at peace with its owner.