The Temple of the Sun is a temple that was controlled by the First Born at the height of their power. Among other features it contains a slow-turning shaft that rotates its position once a year, presumably intended to serve as a calendar as well as a prison.
The temple is located within the inner court of the Temple of Issus and has a thin spire that rises far above the spires and minarets of the greater temple that surrounds it. The sun temple is made of gold, wrought in the most wondrous and fanciful designs and inlaid with precious gemstones.
Beneath the temple, in the ground, is located the main portion of the structure consisting of 687 circular prison chambers (one for each day of the Martian year), one below another. To each chamber a single corridor leads through solid rock from the pits below. As the entire temple rotates once with each revolution of Barsoom about the sun, once each year the entrance to each separate chamber comes opposite the mouth of the corridor that forms its only link to the outside world.
At the subterranean base of the temple is a large circular vault of white marble, the walls inlaid with gold hieroglyphs, and dominated by the great slowly rotating shaft that extends from floor to ceiling. Other than the keys which are guarded by the keeper of the keys, entrance to the shaft may be gained by shining a radium flashlight into a pinhole lock in a concealed door of the shaft using a three-step formula. First, the light must shine at an intensity level of three radium units for a length of time of fifty tals, then at one radium unit for one xat, and lastly at nine units for twenty-five tals. Inside the shaft is a spiral stairway leading upward past the inner walls of the prison cells.
Gaining entrance to the vault itself is made more difficult by certain security measures including a labyrinth of transparent crystal and a chamber infested with venomous snakes and other reptiles.