The governing body of such sewage district shall have the power to construct and maintain sewers with appurtenances thereof, through, under, across or along any street or public highway, and across any vacant property, to a connection with any creek, ravine or river within five miles of the township boundary, and to build, extend, operate and maintain sewage-disposal plants at any point along or near the line of such sewer; and for this purpose the right of eminent domain is hereby granted: Provided, however, That the governing body of such sewage district shall first obtain the written approval of the governing body of any city before constructing improvements in such city.