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.
Cuneiform
Carsten Niebuhr brought the first reasonably complete and accurate copies of the inscriptions at Persepolis to Europe in 1767. Bishop Friedrich Münter of Copenhagen discovered that the words in the Persian inscriptions were divided from one another by an oblique wedge and that the monuments must belong to the age of Cyrus and his successors. One word, which occurs without any variation towards the beginning of each inscription, he correctly inferred to signify "king". By 1802 Georg Friedrich Grotefend had determined that two kings' names mentioned were Darius and Xerxes (but in their native Old Persian forms, which were unknown at the time and therefore had to be conjectured), and had been able to assign correct alphabetic values to the cuneiform characters which composed the two names. Although Grotefend's Memoir was presented to the Göttingen Academy of Sciences and Humanities on September 4, 1802, the Academy refused to publish it; it was subsequently published in Heeren's work in 1815, but was overlooked by most researchers at the time.