The Indianapolis / City as Living Laboratory (I/CaLL) project was a civic collaboration that used the city of Indianapolis as an informal science learning (ISL) environment. The 21 Urban Water Science Concepts Resource Handbook is designed for all people who are interested in exploring science topics related to urban waterways, particularly in Indianapolis. Specifically, educators, artists, and community members in Indianapolis may find this publication useful. With a small amount of extra research for examples in their area of interest, urban environmental educators across the country will