The Back Bay Fens, often called The Fens, is a parkland and urban wild in Boston, Massachusetts, in the United States. It was established in 1879. Designed by Frederick Law Olmsted to serve as a link in the Emerald Necklace park system, the Fens gives its name to the Fenway-Kenmore neighborhood. History The Fens is a large picturesque park that forms part of Boston's Emerald Necklace. It is essentially an ancient spot of saltwater marshland that has been surrounded by dry land, disconnected from the tides of the Atlantic Ocean, and landscaped into a park with fresh water within. The park is also known as the Fens or the Fenway. The latter term can also refer to either the surrounding neighborhood or the parkway on its southern border. When Boston was settled in the early 17th century the Shawmut Peninsula on which it was built was connected to Roxbury by a spit of sandy ground called "The Neck." The adjacent area of marshland to the west was a tidal flat of the Charles River. The area became malodorous with time as it became tainted with sewage from the growing settlement. For the dual purpose of eliminating the health and aesthetic problem created by the polluted bay waters and creating new and valuable Boston real estate, a series of land reclamation projects was begun in 1820 and continued for the rest of the century. The filling of present-day Back Bay was completed by 1882. Filling reached Kenmore Square in 1890 and finished in the Fens in 1900. These projects more than doubled the size of the Shawmut Peninsula. Olmsted's challenge was to restore the spot of marsh which was preserved into an ecologically healthy place that could also be enjoyed as a recreation area. Combining his renowned landscaping talents with state-of-the-art sanitary engineering, he turned a foul-smelling tidal creek and swamp into "scenery of a winding, brackish creek, within wooded banks; gaining interest from the meandering course of the water." Olmsted designed the Fens to be flushed by the tides twice daily. However, in 1910 a dam was constructed at Craigie's Bridge, closing the Charles River estuary to the ocean tides and forming a body of freshwater above the dam. Thus, the Fens became a freshwater lagoon regularly accepting storm water from the Charles River Basin. Soon after, noted landscape architect Arthur Shurcliff, a protégé of Olmsted, added new features such