Civilization.  The very notion and idea you have come to despise.  Unfortunately, we must live amongst it, near it, or in spite of it.

Civilization Points (CP) are areas, either represented on the game map, or mentioned as you discover them; that stand for concentrated populations that have taken-up permanent residence in a given Grid.  They range from miniscule hamlets of just a few families, up to massive, cobbled roads housing thousands in a Metropolis.

CPs are divided into two types:
Types of Civilization Points (CPs)
On-Map CP (OMCP)Those which are represented on the Game Map
Off-Map CP (OFFMCP)Those which are not represented on the Game Map

Regardless of the type; there can only be one CP per Grid.  Once a CP is discovered in a Grid: that becomes that Grid's CP for the remainder of the game.  If this CP is destroyed: it is removed forever and never replaced.

The Size of the CP reflects how easy it is to find goods to purchase, whether anyone will purchase your goods, or if Units are available to Recruit.

Diplomacy with CPs
SizeBonus
Hamlet+1
Village+2
Settlement+3
Small Town+4
Large Town+6
Small City+8
Large City+12
Metropolis+15

As you can see from the chart-above: it is much easier to successfully conduct Diplomacy with larger CPs.  Your general anonymity combined with the multitude of opportunities means that you are more likely to find what you need.  However, there are some distinctions between these two that will be covered in their separate wiki pages.

OMCP
OFFMCP

CPs different significantly from landmarks - but, represent places to which you can journey to learn more about the story of the world and gain greater insight to events that are happening.

Landmarks