Nishiwaki is a city located in Hygo Prefecture, Japan. The city calls itself "The Navel of Japan (Nihon no Heso)." Located at the crossing of the 135° East meridian and the 35° North parallel, the city's Nihon no Heso Park marks the center of the nation. JR West operates Nihon Heso Station on the Kakogawa Line (in addition to other stations in Nishiwaki). As of May 1, 2011 the city has an estimated population of 43,970, with a household number of 16,490 and a population density of 331.92 persons per Square kilometer. The total area is 132.47 Square kilometers. The city was founded on April 1, 1952 and is the sister city of Renton, Washington, U.S.A.