Areas of the physical environment, typically a piece of real estate previously owned and used by a chemical or related manufacturing or processing business, that have become contaminated to such an extent that they are not granted permits for use in the town or city where they are located. However, brownfields may be able to be "rehabilitated" or used wisely, in such a way as to minimize dangers to new users. These are brownfields. Brownfield utilization can be extremely important for any given town or city because the site may be at the heart of the industrial center of the old city or town. For an example of a city where the corporation left the site and refuses to permit brownfield use, see Schenectady, NY. For a site that is the opposite and has had corporate cooperation with local authorities and environmental engineers see "Positive Example."