Zarach (Persian: زارچ‎‎, also Romanized as Zārach or Zārch; also known as Zarej and Zārj) is a city in and the capital of Zarach District, in Yazd County, Yazd Province, Iran. At the 2006 census, its population was 9,979, in 2,447 families.Zarch is situated 5 km west of the Yazd city. This city has the longest and oldest Kariz in the world with length 71 km and over 3,000 years of age in the world.