▁been ▁found ▁in ▁northern ▁Iran . ▁ ▁The ▁Q an ats ▁mostly ▁came ▁in ▁from ▁higher ▁elev ations , ▁and ▁were ▁split ▁into ▁a ▁distrib uting ▁network ▁of ▁smaller ▁under ground ▁can als ▁called ▁kar iz ▁when ▁reaching ▁the ▁city . ▁Like ▁Q an ats , ▁these ▁smaller ▁can als ▁were ▁below ▁ground ▁( ~ 2 0 ▁steps ), ▁and ▁were ▁built ▁such ▁that ▁they ▁were ▁very ▁difficult ▁to ▁cont amin ate . ▁These ▁under ground ▁aqu ed uct s , ▁built ▁thousands ▁of ▁years ▁ago ▁suffer ▁no ▁ev ap oration ▁loss ▁and ▁are ▁ide ally ▁su ited ▁for ▁drink ing ▁water ▁since ▁there ▁is ▁no ▁poll ution ▁danger . ▁ ▁But ▁with ▁the ▁further ▁growth ▁of ▁the ▁city ▁in ▁Pers ian ▁lands , ▁even ▁the ▁Q an ats ▁could ▁not ▁respond ▁to ▁the ▁needs ▁of ▁residents . ▁That ▁is ▁when ▁some ▁wealth y ▁inhabitants ▁started ▁building ▁private ▁res er voir s ▁called ▁ab ▁an bar ▁( Pers ian ▁ آ ب ▁ ا ن ب ا ر ). ▁ ▁In ▁the ▁middle ▁of ▁the ▁tw enti eth ▁century , ▁it ▁is ▁estimated ▁that ▁approximately ▁ 5 0 , 0 0 0 ▁q an ats ▁were ▁in ▁use ▁in ▁Iran , ▁each ▁commission ed ▁and ▁maintained ▁by ▁local ▁users . ▁ ▁Of ▁these ▁only ▁ 2 5 , 0 0 0 ▁remain ▁in ▁use ▁as ▁of ▁ 1 9 8 0 . ▁ ▁One ▁of ▁the ▁oldest ▁and ▁largest ▁known ▁q an ats ▁is ▁in ▁the ▁Iran ian ▁city ▁of ▁Gon abad ▁which