Kenilworth Park & Aquatic Gardens - http://www.nps.gov/keaq/

Kenilworth Park and Aquatic Gardens constitutes some 700 acres and is part of Anacostia Park. The Park includes the "Gardens", Kenilworth Marsh, ballfields and recreational facilities. The origins of Kenilworth Park and Aquatic Gardens lie not only in the 1791 L'Enfant Plan for the District of Columbia, but also the McMillan Plan of 1901 which specifically recommended extension of public parkland along both sides of the Anacostia River.
The Kenilworth Aquatic Gardens is the only National Park Service site devoted to the propagation and display of aquatic plants. The Gardens were begun as the hobby of Civil War veteran and operated for 26 years as a commercial water garden. In 1938, the Gardens were purchased by the Federal Government. It was at that time that the facility ceased operating as a commercial enterprise and became part of the National Park system.