The Fire Temple was a five-tiered pagoda built atop a craggy hill on Crescent Island in the outer Fire Nation. It was maintained by the Fire Sages, and was closely associated with AvatarRoku, who studied there for many years to master the Avatar State. The ancient temple used mechanisms that required firebending to operate; for example, the sanctuary door could only be opened by five simultaneous fire blasts.
The Fire Temple was originally founded as a refuge for the Fire Sages, the Fire Nation's religious authority, on the outermost island of the Fire Nation archipelago. The temple was built on Crescent Island so that its placing would align with the sun's location on solstices and equinoxes.
In his quest to become a Fully Realized Avatar, Avatar Roku took shelter in this temple, where he eventually mastered the Avatar State. However, during the process, he destroyed the temple, and was later forced to rebuild it. During the reconstruction, Avatar Roku carved a series of secret passages beneath the structure.
The temple was destroyed again when Avatar Roku manifested himself through Aang's body to defeat the Fire Nation soldiers stationed outside the sanctuary.
The sanctuary was built to receive a shaft of sunlight through a giant ruby and cast a spot of light within the sanctuary. At sundown on the winter solstice, the spot of sunlight would reach and illuminate Avatar Roku's statue, making it possible to communicate with him. When Avatar Roku was alive, the Fire Sages used the sanctuary to communicate with him on the solstice, but after his demise, only Aang was able to communicate with Avatar Roku. The sanctuary's massive door protected the sanctuary from intruders. These doors could only be opened by either a Fully Realized Avatar or with five simultaneous fire blasts.