The Council shall provide for the care, supervision, control and improvement of public highways, bridges, streets, avenues, alleys, sidewalks, public grounds, aqueducts and viaducts within the City, and shall cause them to be kept open, in repair and free from nuisance, and it may order any street, alley, or public highway to be opened, straightened, altered, diverted, narrowed, widened or vacated.