The visual cortex of animals such as cats, monkey and ferrets contains multiple maps of features of visual scenes, including visual field position, orientation, direction, ocular dominance and spatial frequency. The complex relationships between these maps provide clues to the strategies the cortex uses for representing and processing information. We have modelled the combined development of these maps, based on the idea that they may attempt to optimize a trade-off between coverage and continuity. Besides normal development, these models also reproduce some of the phenomena observed when animals are raised in abnormal visual environments. Together these results argue that mathematical modelling can make an important contribution to our understanding of visual development.