This chapter surveys the parameters of Roman agriculture including climate, geography, demography, and especially botany. The study of the Roman climate is very much in its infancy but there seems to be an emerging consensus that there was a period of relative warmth in the late Republic and early Empire. This "Roman Climate Optimum" or "Roman Warm Period" began in the third century bce and lasted until the second century ce. Familiarity with the major crops of Roman agriculture is essential if people want to understand the economic behavior of Roman farmers. Farmers who chose to grow a variety of cereals, either to minimize risk or to take advantage of different soils and situations, could need several different kinds of equipment and, ideally, separate storage areas for the crops. In order to understand the economic behavior of Roman farmers, it is essential to first have an understanding of the physical environment in which they operated.