Fire is seen as the supreme symbol of purity, and sacred fires are maintained in Fire Temples (Agiaries). These fires represent the light of God (Ahura Mazda) as well as the illuminated mind and are never extinguished. No Zoroastrian ritual or ceremony is performed without the presence of a sacred fire.

A fire temple in Zoroastrianism is the place of worship for Zoroastrians, often called Dar-e Mehr (Persian) or Agiyari (Gujarati). In the Zoroastrian religion, fire (Atar) together with clean water (Aban), are agents of ritual purity. Clean, white "ash for the purification ceremonies [is] regarded as the basis of ritual life," which, "are essentially the rites proper to the tending of a domestic fire, for the temple [fire] is that of the hearth fire raised to a new solemnity".

The oldest remains of what has been identified as a fire-temple are those on Mount Khajeh, near Lake Hamun in Sistan. Only traces of the foundation and ground-plan survive and have been tentatively dated to the 3rd or 4th century BCE. The older ones are the numismatics pieces of evidence such as the Sassanian Coinage. The Coins depict the king’s portrait on the obverse and different types of Fire Altars on the reverse.

Image Courtesy: Wikipedia