door, while the others are left as holeless blind windows. The structure stands on a three-tiered platform. The first tier is above the ground, and the tower is high including the triple tiers or stairs of its platform. The base is square-shaped, with each side approximately long. The ceiling of the structure is smooth and flat on the inside, but its roof has a bilateral slope that begins from the line in the middle of the rooftop on the outside, creating the pyramid-like appearance previously mentioned. The doorway is high and wide and at one point had a very heavy two-panel door which is now missing. There are carved-out notches for the upper and lower heels of each door panel in the stone frame which are visible to modern observers. Some have assumed that the door would have been made of wood, but a stone door, very similar to the remains of the one found in Ka'ba-ye Zartosht, exists in Solomon's Prison in Pasargadae, which indicates that both doors were made of stone. The doorway leads to a single interior room. This space is quadrangular, has an area of , and is high, with the thickness of its walls being between . History The Ka'ba-ye Zartosht is undoubtedly from the Achaemenid era. Much of the available evidence shows that it was built in the early Achaemenid era; the most important evidence for this dating is as follows: Using black stone on a white background is one of the features of Pasargadian architecture. The dovetail joints are found mostly in the periods of Darius I and Xerxes I, and the way the stones are aligned is similar to the primary structures of Persepolis. The doorway and door of the structure is similar to those of the Achaemenid shahs' mausoleums, all of which have used the design of Darius I's mausoleum. The masonry, which lacks mortar or ordering, resembles the first parts of the platform of Persepolis that were constructed in Darius I's period. Especially, the inscription on the lower part of the southern wall of Persepolis is almost the same size as the stones forming the ceiling of Ka'ba-ye Zartosht. Carsten Niebuhr, who had visited the structure in 1765, writes: "Opposite the mountain that has the mausoleums and petroglyphs of Rostam's braveries, a small structure is built of white stone that is covered by only two pieces of large stones." Jane