Persepolis
Darius I built the greatest palace at Persepolis on the western side of platform. This palace was called the "Apadana". The King of Kings used it for official audiences. The work began in 518 BC, and his son, Xerxes I, completed it 30 years later. The palace had a grand hall in the shape of a square, each side long with seventy-two columns, thirteen of which still stand on the enormous platform. Each column is high with a square Taurus (bull) and plinth. The columns carried the weight of the vast and heavy ceiling. The tops of the columns were made from animal sculptures such as two-headed lions, eagles, human beings and cows (cows were symbols of fertility and abundance in ancient Iran). The columns were joined to each other with the help of oak and cedar beams, which were brought from Lebanon. The walls were covered with a layer of mud and stucco to a depth of 5 cm, which was used for bonding, and then covered with the greenish stucco which is found throughout the palaces.
Persepolis
About 200 BC, the city of Estakhr, five kilometers north of Persepolis, was the seat of the local governors. From there, the foundations of the second great Persian Empire were laid, and there Estakhr acquired special importance as the center of priestly wisdom and orthodoxy. The Sasanian kings have covered the face of the rocks in this neighborhood, and in part even the Achaemenid ruins, with their sculptures and inscriptions. They must themselves have been built largely there, although never on the same scale of magnificence as their ancient predecessors. The Romans knew as little about Estakhr as the Greeks had known about Persepolis, despite the fact that the Sasanians maintained relations for four hundred years, friendly or hostile, with the empire.