british columbia is customarily divided into three main regions, the interior, the coast and the lower mainland (though the last-named is technically part of the coast). these are broken up by a loose and often overlapping system of cultural-geographic regions, often based on river basins but sometimes spanning them. examples of the former would be the kootenays, the okanagan, and the chilcotin, while of the latter would be the lillooet country and cariboo. important subareas of these include the fraser valley, part of the lower mainland, the fraser canyon (which overlaps with various regions) and the robson valley, which is the uppermost basin of the fraser river southeast of prince george. vancouver island is seen as its own region within the coast, as are the haida gwaii (queen charlotte islands) and the gulf islands.