The Albany-Millersburg Talking Water Gardens - In 2010, it was the first engineering project of its kind in the United States. It's a constructed treatment wetland. It's designed to naturally filter and provide additional levels of treatment for municipal and industrial wastewater flow. It's the final step before returning this treated water safely to the Willamette River. The city website says: "The project is an engineered wetlands facility designed to reduce water temperature, restore riparian forest and wetlands, promote wildlife habitat and create a living laboratory that brings wetland science to life. It creates a new natural attraction for Albany area visitors."
Lovely image of an intentional simulation of a natural process.