A fact of life for people who live by gathering plant and animal foods and hunting animals is the changing availability of these resources from season to season. It appears that in most regions Upper Paleolithic groups were seasonally mobile, following a systematic seasonal round related to changes in the location and availability of food resources. However, in some regions of great topographic diversity where many plant and animal habitats were easily accessible, these seasonal movements may have been few and over relatively short distances. For example, here in the small French valley known as the Gorge d'Enfer, topographic diversity within a short distance is evident. At bottom is the floodplain; at center is a gently sloping valley ascending to the plateau at top. There are seven known Upper Paleolithic sites in this valley.