Where an area of real property owned by a municipality is bounded by a wall, fence or other structure which has gates or other lockable entrances, the municipality shall notify those public agencies within the municipality which provide ambulance, fire and police services of the location of such gates and entrances. A key to each such enclosed area shall be provided by the municipality to the ambulance, fire company and police department which is closest to the enclosed area. For purposes of this section, the words “real property” shall include all unimproved land only and shall not include buildings.