Certain buildings are described as having a positive effect on certain types of "nearby" buildings -- such as a Fire Station in "Cat-in-tree" mode improving housing quality, or the Salt Mine improving production of "nearby" canneries, or the upgraded fish farms in certain modes improving "nearby" seafood restaurants.
It doesn't really mention how far away you can build said buildings and still have it count as "nearby", however. Does anyone know or have some hard data on the maximum radius of "nearby" ?