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.
Achaemenid Empire
The Persians from whom Cyrus hailed were originally nomadic pastoralists in the western Iranian Plateau and by 850 BC were calling themselves the "Parsa" and their constantly shifting territory "Parsua", for the most part localized around Persis. As Persians gained power, they developed the infrastructure to support their growing influence, including creation of a capital named Pasargadae and an opulent city named Persepolis.
Begun during the rule of Darius I "the Great" and completed some 100 years later, Persepolis was a symbol of the empire serving both as a ceremonial centre and a centre of government. It had a special set of gradually progressive stairways named "All Countries" around which carved relief decoration depicted scenes of heroism, hunting, natural themes, and presentation of the gifts to the Achaemenid kings by their various subjects, possibly during the spring festival, Nowruz. The core structure was composed of a multitude of square rooms or halls, the biggest of which was called "Apadana". Tall, decorated columns welcomed visitors and emphasized the height of the structure. Later on, Darius also utilized Susa and Ecbatana as his governmental centres, developing them to a similar metropolitan status.