The Council shall declare by ordinance at the time of acquisition the intended use of any acquired land. All parks, undeveloped lands open to the public, and lands for the use of the public, owned or acquired by the City shall be restricted solely to that purpose intended at the time of acquisition or later designated. Any change in the use, any sale or other disposition of any of these properties must be approved by a three-fifths (3/5) majority vote of the City electors at a regular or special election.