The Ka'ba-ye Zartosht, meaning the "Cube of Zoroaster", is a 5th century B.C.E. Achaemenid-era tower-like construction. This enigmatic structure is one of many surviving examples of the Achaemenid architectural design.

The square tower is constructed of white limestone blocks, that are held in place by iron cramps. Mortar was not used in its construction. Each face of the building is decorated with slightly recessed false windows of black limestone.