Paul S.
Google
Take the tour! Not only is it an great look into how water treatment works (and hardly smelly at all, thanks to the odor management system), but the management of sewage in urban areas is one of the greatest health achievements of all time and Deer Island is, depending on what measure you use, the largest or second largest wastewater treatment plant in terms of volume of water treated.
(Also, if you work for Firaxis, this should be a World Wonder in the next Civilization game. Thanks!)