About Persepolis (from Wikipedia):
Persepolis was the ceremonial capital of the Achaemenid Empire (ca. 550–330 BC). It is situated 60 km northeast of the city of Shiraz in Fars Province, Iran. The earliest remains of Persepolis date back to 515 BC. It exemplifies the Achaemenid style of architecture. UNESCO declared the ruins of Persepolis a World Heritage Site in 1979.
Archaeological evidence shows that the earliest remains of Persepolis date back to 515 BC. André Godard, the French archaeologist who excavated Persepolis in the early 1930s, believed that it was Cyrus the Great who chose the site of Persepolis, but that it was Darius I who built the terrace and the palaces. Inscriptions on these buildings support the belief that they were constructed by Darius.
The function of Persepolis remains rather unclear. It was not one of the largest cities in Persia, let alone the rest of the empire, but appears to have been a grand ceremonial complex, that was only occupied seasonally; it is still not entirely clear where the king’s private quarters actually were. Until recent challenges, most archaeologists held that it was especially used for celebrating Nowruz, the Persian New Year, held at the spring equinox, and still an important annual festivity in modern Iran. The Iranian nobility and the tributary parts of the empire came to present gifts to the king, as represented in the stairway reliefs.
After invading Achaemenid Persia in 330 BC, Alexander the Great sent the main force of his army to Persepolis by the Royal Road. He stormed the “Persian Gates”, a pass through modern-day Zagros Mountains. There Ariobarzanes of Persis successfully ambushed Alexander the Great’s army, inflicting heavy casualties. After being held off for 30 days, Alexander the Great outflanked and destroyed the defenders. Ariobarzanes himself was killed either during the battle or during the retreat to Persepolis. Some sources indicate that the Persians were betrayed by a captured tribal chief who showed the Macedonians an alternate path that allowed them to outflank Ariobarzanes in a reversal of Thermopylae. After several months, Alexander allowed his troops to loot Persepolis.
Persepolitan architecture is noted for its use of the Persian column, which was probably based on earlier wooden columns. Architects resorted to stone only when the largest cedars of Lebanon or teak trees of India did not fulfill the required sizes. Column bases and capitals were made of stone, even on wooden shafts, but the existence of wooden capitals is probable. In 518 BC, a large number of the most experienced engineers, architects, and artists from the four corners of the universe were summoned to engage and with participation, build the first building to be a symbol of universal unity and peace and equality for thousands of years.
The buildings at Persepolis include three general groupings: military quarters, the treasury, and the reception halls and occasional houses for the King. Noted structures include the Great Stairway, the Gate of All Nations, the Apadana, the Hall of a Hundred Columns, the Tripylon Hall and the Tachara, the Hadish Palace, the Palace of Artaxerxes III, the Imperial Treasury, the Royal Stables, and the Chariot House.