Commercial buildings are buildings that are used for commercial purposes, and include office buildings, warehouses, and retail buildings (e.g. convenience stores, 'big box' stores, and shopping malls). In urban locations, a commercial building may combine functions, such as offices on levels 2-10, with retail on floor 1. When space allocated to multiple functions is significant, these buildings can be called multi-use. Local authorities commonly maintain strict regulations on commercial zoning, and have the authority to designate any zoned area as such; a business must be located in a commercial area or area zoned at least partially for commerce.