Zarach is a city in the Central District of Zarach County, Yazd province, Iran, serving as capital of both the county and the district. The city is …Zarach is a city in the Central District of Zarach County, Yazd province, Iran, serving as capital of both the county and the district. The city is 5 km west of the city of Yazd. Zarach has the longest and oldest kariz in the world, with a length of 71 km and is over 3,000 years of age.