The Romans constructed numerous aqueducts to serve any large city in their empire, as well as many small towns and industrial sites. The city of Rome had the largest concentration of aqueducts, with water being supplied by eleven aqueducts constructed over a period of about 500 years. They served drinking water and supplied the numerous baths and fountains in the city, as well as finally being emptied into the sewers, where the once-used gray water performed its last function in removing waste matter.