Sun and Moon cults were probably represented at the Circus from its earliest phases. Their importance grew with the introduction of Roman cult to Apollo, and the development of Stoic and solar monism as a theological basis for the Roman Imperial cult. In the Imperial era, the Sun-god was divine patron of the Circus and its games. His sacred obelisk towered over the arena, set in the central barrier, close to his temple and the finishing line. The Sun-god was the ultimate, victorious charioteer, driving his four-horse chariot ("quadriga") through the heavenly circuit from sunrise to sunset. His partner Luna drove her two-horse chariot ("biga"); together, they represented the predictable, orderly movement of the cosmos and the circuit of time, which found analogy in the Circus track. In Imperial cosmology, the emperor was Sol-Apollo's earthly equivalent, and Luna may have been linked to the empress. Luna's temple, built long before Apollo's, burned down in the Great Fire of 64 AD and was probably not replaced. Her cult was closely identified with that of Diana, who seems to have been represented in the processions that started Circus games, and with Sol Indiges, usually identified as her brother. After the loss of her temple, her cult may have been transferred to Sol's temple on the dividing barrier, or one beside it; both would have been open to the sky.