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.
Iranian peoples
Later on, in 550 BCE, Cyrus the Great, would overthrow the leading Median rule, and conquer Kingdom of Lydia and the Babylonian Empire after which he established the Achaemenid Empire (or the First Persian Empire), while his successors would dramatically extend its borders. At its greatest extent, the Achaemenid Empire would encompass swaths of territory across three continents, namely Europe, Africa and Asia, stretching from the Balkans and Eastern Europe proper in the west, to the Indus Valley in the east. The largest empire of ancient history, with their base in Persis (although the main capital was located in Babylon) the Achaemenids would rule much of the known ancient world for centuries. This First Persian Empire was equally notable for its successful model of a centralised, bureaucratic administration (through satraps under a king) and a government working to the profit of its subjects, for building infrastructure such as a postal system and road systems and the use of an official language across its territories and a large professional army and civil services (inspiring similar systems in later empires), and for emancipation of slaves including the Jewish exiles in Babylon, and is noted in Western history as the antagonist of the Greek city states during the Greco-Persian Wars. The Mausoleum at Halicarnassus, one of the Seven Wonders of the Ancient World, was built in the empire as well.