In addition to other powers, the mayor and council of cities of the third class are hereby authorized and empowered to acquire by gift, devise, purchase or condemnation, within such cities or within a mile thereof, such real and personal property as may be necessary or desirable for the purpose of the erection or construction of dams, lake and flood protection systems, bathhouses, therapeutic bathhouses, mineral water vending houses and in connection therewith, auditoriums and lecture rooms and for the laying of pipelines for the distribution of mineral waters and to so acquire, improve and operate mineral springs and wells, and to construct all necessary and appropriate buildings and works therefor, and to do any and all things necessary to maintain and operate said properties so acquired and constructed as a self-liquidating revenue producing public project, and for that purpose to lease or convey the same; provided such properties shall be so acquired, constructed and thereafter maintained and operated without increasing the indebtedness of such city and shall not be paid for, maintained or operated by taxes, either general or special.