Well to find the way to the City of Truth, I would ask the citizen "If I were to ask you which way leads to the City of Lies, which way would you point.?” because think about If the citizen is from the City of Lies, they will point to the City of Truth, because they are lying about which way leads to the City of Lies. If the citizen is from the City of Truth, they will point to the City of Lies, because they are telling the truth about which way leads to the City of Lies.