Biome

A biome is a contiguous group of tiles which share similar ecological conditions, including temperature, precipitation, and local fauna.

A civ's units may struggle to survive outside of its native biome, particularly if it is one where conditions are more extreme. Types of animals, available resources, elevation variability (i.e. flattness or hilliness), and weather conditions can all vary signifigantly between biomes.

Some biomes tend to be smaller or larger than others, but even the smallest biome is large enough to support a small civilization.