The New River was an aqueduct, built between 1609 and 1613 by City banker and MP Sir Hugh Myddelton. The river was the main source of fresh water from Hertfordshire to north London and the City until around 1990. The water flowed into the Round Pond at New River Head, where a water house controlled supply to surrounding houses. A further reservoir, the Upper Pond, was constructed in 1709 and later developed as Claremont Square. From the 1680s, natural springs around the reservoirs were developed as commercial spas for their medicinal properties. The water house was demolished to make way for the headquarters of the Metropolitan Water Board, which took over from the New River Company in 1904. The grade II listed building, built in 1919 on part of the Inner Pond, is now in private residential use (converted 1997-8), and its garden occupies the site of the Outer Pond.