Wetlands are areas where water temporarily or permanently saturates the ground. Wetlands are important to us for multiple reasons--they are filters for the water as it moves to its next phase in the collection process, and it is a habitat for many species, some of which are endangered.
Lexington, KY, had a major clean water problem. During heavy rains, the runoff would overflow the storm and sanitary sewers causing waste to be sent through one of the seven area watersheds, making its way to local streams. The discharge was so bad that the Environmental Protection Agency and Commonwealth of Kentucky sued the city for violations of the Clean Water Act. Under a Consent Decree, finalized in January 2011, the city was required to fix problems with the sanitary and storm sewer systems over the next several years. Across the city, multiple projects have been undertaken to remediate the water problems caused by excessive runoff from paved surfaces as well as outdated and improperly functioning infrastructure.
One such project is the Gainesway Pond and Wetland in Gainesway Park. 
At a cost of over $800,000, the pond was revitalized and made into a functioning wetland and real world classrom for students. The wetland itself was constructed, along with a boardwalk and amphitheater for real world student learning. School children make observations of the water quality (pH, temperature, and dissolved oxygen and nitrate levels) seeing the impact that this urban wetland has on improving their water supply.
How does it work? At the nearby parking area, N 37 58.887 W 084 28.915 You will see two manhole covers with plants growing out of them. 
In addition to the solid traps to prevent waste from entering the water, these plants filter water running downhill from the paved surfaces and help cool the water and filter the waste like gasoline and sediment that works its way into the water supply. The wetland further filters this water through natural biological processes aided by some constructed filters. From here, the water works its way to the West Hickman Watershed, and beyond. The wetland also provides habitat for insects, birds, and aquatic invertebrates.
Questions for consideration at the site (email the owner at profile link above):
1) Based on your observations at the site, why do you think this area retains water?
2) What features of the location help to filter the water before the water moves into the local streams?
3) Estimate the dimensions of the wetland to your east.
4) What large body of water is the ultimate destination of the water from this wetland?
5) Post an optional picture of yourself with the wetlands as a backdrop.