The board of aldermen shall have power to create, open and improve any public square, public park, street, avenue, alley or other highway, old or new, and also to vacate or discontinue the same whenever deemed necessary or expedient; provided, that all damages sustained by the citizens of the city or the owners of the property therein shall be ascertained as prescribed in that portion of this chapter relating to the condemnation of private property for public use; and provided further, that whenever any public square, street, avenue or alley, or other highway, shall be vacated, the same shall revert to the owners of the adjacent lots in proportion as it was taken from them; and when the grade of any street or alley shall have been once established by ordinance, it shall not be lawful to change such grade without making compensation to all persons owning real estate on such street or square, avenue, alley or other highway, who may be damaged by such change of grade, to be determined and governed in all respects, with reference to benefit and damages, as is provided in sections 88.667 to 88.773.