After the bonds of the district and all interest thereon have been paid the property shall continue to be used as public parking places. However, such use may be discontinued as to such property or any portion thereof if the legislative body, after public hearing following such notice thereof as the legislative body may prescribe, determines by a four-fifths vote of all its members that the public interest and necessity and the needs of the district no longer require that such property, or such portion thereof, be used as public parking places. Thereafter the property as to which such determination is made may be used by the city for any public purpose or it may be sold as other city property is sold when no longer needed for a public purpose. If any ad valorem assessment has been levied upon the real property in the district as provided in this part, then the proceeds of such sale shall be used to make refund of such assessments to the then owner of each parcel of real property which has been so assessed in the proportion which the total assessments levied upon such parcel bears to the total of all such assessments, but no refund as to any parcel shall exceed the total assessments theretofore paid in respect of said parcel, and any portion of the proceeds remaining after such refunds have been made shall be placed in the general fund of the city.