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.
Battle of the Persian Gate
The defeat of Ariobarzanes's forces at the Persian Gate removed the last military obstacle between Alexander and Persepolis. Upon his arrival at the city of Persepolis, Alexander appointed a general named Phrasaortes as successor of Ariobarzanes. Alexander seized the treasury of Persepolis, which at the time held the largest concentration of wealth in the world, and guaranteed himself financial independence from the Greek states. Four months later, Alexander allowed the troops to loot Persepolis, kill all its men and enslave all its women, perhaps as a way to fulfill the expectations of his army and the Greek citizens, or perhaps as a final act of vengeance towards the Persians. This destruction of the city can be viewed as unusual as its inhabitants surrendered without a fight and Alexander had earlier left Persian cities he conquered, such as Susa, relatively untouched. In May 330 BC, Alexander ordered the terrace of Persepolis, including its palaces and royal audience halls, to be burned before he left to find Darius III. Sources disagree as to why he ordered the destruction: it could have been a deliberate act of revenge for the burning of the Acropolis of Athens during the Second Greco-Persian War, an impulsive, drunken act, or it could have been out of Alexander's supposed anger over not being recognized as the legitimate successor to Darius III.