Not every city is built on flat, level ground. Historically speaking, most city sites were chosen because of some form of advantageous terrain which made the area especially fertile or defensible. When exploring a hex, either personally or as part of an Exploration Edict, if your surveyors spend double the normal amount of exploration time required on the Terrain and Terrain Improvements table in the published rules, they can seek out an ideal city site for defense, trade, or simply abundant production. After this extended exploration, the explorers must make a Knowledge (geography) check, dividing the result by 20 (rounding down). The result is the number of natural advantages they discover at the optimal settlement site in the hex. If the check result is sufficiently high to provide more than one natural advantage, you may select the same advantage more than once; the effects stack. If no settlement is established in the hex, these natural advantages confer no benefit.
Fertile Land and Abundant Water:
Situated over clear natural springs, aquifers, oases, with unusually rich soil, your settlement has an easy time making the land bloom and grow.
Benefit: Stability +1.
Situated at the foot of a pass, alongside a navigable river or deep-water harbor, or sited along a longstanding trade route, your settlement has a leg up on the competition in matters of trade.
Benefit: Economy +1.
Situated on a natural rise, or the foot of a cliff, or a confluence or bend in a river system, your settlement is easier to defend from attackers.
Benefit: Defense +1.