Yazd [Iran, 2004] Zoroastrians, followers of the world's oldest monotheistic religion, believe both fire and earth must be kept pure. That means bodies cannot be cremated or buried, so until the 1960s their dead were placed in the hilltop "Tower of Silence" in the background to be pecked clean by vultures. These days Iran's Zoroastrians are buried in concrete-lined graves to avoid contaminating the earth. The brick dome in the foreground covers a water cistern; the "wind towers" funnel breezes into the cistern to keep the water cool.