What is the name of the rear room in the Parthenon's cella?

The rear room in the Parthenon’s cella was called the opisthodomos.

The Greek term means “back room” or “rear chamber.” In a classical temple plan, the opisthodomos corresponded broadly to the pronaos, the porch or vestibule at the front. This rear space helped give the building a balanced, symmetrical appearance when viewed from outside.

In the Parthenon, the cella was divided into two distinct compartments. The eastern room, or naos, housed the famous chryselephantine statue of Athena Parthenos, while the western opisthodomos was associated with the treasury of the Delian League. It had four interior columns and was wider than the front room, an unusual feature linked to Cycladic architectural traditions.

The terms can be confusing because naos and cella may both refer to a temple’s main inner chamber, while pronaos means the front porch. Tholos, by contrast, describes a circular building or room, not the Parthenon’s rear chamber. The opisthodomos was not simply a storage closet in every Greek temple; its exact use varied by site and period.