Rey Fire Temple which is known as Mil Hill among the local people is located by Tehran-Varamin Road and on a hill between barley lands. Rey is referred in the holy book of Zoroastrians as a religious center and this fire temple might have been the center of ancient Rey! There have been active excavations on this hill recently and many works have been achieved by it.
There is a great fire temple on top of the hill that can be seen from distance and the holy fire has always been lit in it. There is tunnel beneath the fire temple which was used to transport the fire. That is because according to Zoroastrian beliefs, holy fire should not be exposed to the sunlight. The tunnel connects the two sides of the hill.
On the other part of the hill, some hill structures have come out of the heart of the ground where many moldings have been found. There is a beautiful treasury of Sassanid moldings in the museum of the hill.