The board of supervisors of any county may, by a four-fifths vote of the members, use or dedicate any portion of any land acquired by the county by means of special assessment proceedings for park purposes, for the erection and maintenance of one or more buildings to house a superior court, or one or more departments or divisions thereof, if the portion of the land to be so used or

dedicated has not been used by the public for park purposes for a period of more than 10 years.