 Since 1974 , Denver and the surrounding jurisdictions have rehabilitated the urban South Platte River and its tributaries for recreational use by hikers and cyclists . The main stem of the South Platte River Greenway runs along the South Platte from Chatfield Reservoir 35 miles ( 56 km ) into Adams County in the north . The Greenway project is recognized as one of the best urban reclamation projects in the U.S. , winning , for example , the Silver Medal Rudy Bruner Award for Urban Excellence in 2001 . 
