Persepolis
It was one of the first Iranian sites to be registered in UNESCO World Heritage List. The Persepolis compound, known to Iranians as Takht-e Jamshid, is a very remarkable example of ancient monuments of Iran.

Persepolis (Persian: Takht-e Jamshīd) is perhaps the best-known archaeological monument of Persia (Iran). Here in the twinkling of an eye we can leave the modern world behind and find ourselves in about 500 BC at the capital of the greatest empire the world had known to that time: the Persian Empire.

 ‘Persepolis’ is the Greek name given to the capital of the Achaemenid dynasty. It means the City of the Persians. Ancient Persians, however, would refer to it as the city of Pārse.Today Persepolis is located a few minutes driving from the city of Marvdasht in Fārs province, 56 km northeast of Shīraz.The geographical site of the Persepolis is also interesting. It is built on the foothills of Rahmat Mountains near the Sīvand River. This place has been regarded as a sacred site from prehistoric times.
The construction of the Persepolis began between 518 and 516 BC upon the order of Darius The Great who transferred the capital of the empire from Pasargadae to this newly established place. The construction continued Darius; successor Xerxes I and Artaxerxes I in the 5th century BC.
At its height the Persian Empire stretched from Greece and Libya in the west to the Indus River in present-day Pakistan in the east. The many nations under the empire’s rule enjoyed considerable autonomy in return for supplying the empire’s wealth. Each year at New Year Festival of Norūz—still celebrated in Iran on the first day of spring—representatives from these nations brought tribute to the king. The Persian kings used Persepolis primarily as a residence and for ceremonies such as the celebration of Norūz.
The site of Persepolis consists of the remains of several monumental buildings on a vast artificial stone terrace about 450 by 300 m (1,480 by 1,000 ft). A double staircase, wide and shallow enough for horses to climb, led from the plains below to the top of the terrace. At the head of the staircase, visitors passed through the Gate of All Nations, a gatehouse guarded by enormous carved stone bulls.
Apadana
 

Massive stone columns supported the Apadana’s roof; 36 were interior columns and another 36 supported verandas on three sides of the building.

The largest building at Persepolis, the Apadana (audience hall), stood to the right of the gatehouse. Archaeologists estimate that it could accommodate 10,000 people. Massive stone pillars supported the Apadana’s roof; 36 were interior pillars and another 36 supported verandas on three sides of the building. Thirteen of these 72 pillars remain standing today. Each pillar rose nearly 20 m (66 ft) high and had vertical channels called fluting carved into it to emphasize this height. At the top of the pillars were capitals elaborately decorated with plant forms, scrolls, and double-headed animals. The animals supported wooden roof beams on their backs. Traces of paint found on pillars bases and other remains suggest that the room was originally brightly colored.
Monumental staircases decorated with elaborate sculpture in relief (raised) led to the Apadana, which stood on an elevated platform. The relief sculpture depicts the ceremonial procession that took place when representatives from the conquered nations brought gifts to the king. The procession is led by Persians and Medes, the peoples whom Cyrus the Great united to found the Persian Empire. After them come delegates bearing gifts. Because the east staircase lay buried beneath ashes and rubble for centuries, its delicately carved relief sculptures remain in excellent condition today.
 
100 Pillars Palace

Throne hall also known as the Hundred-Column Hall after the 100 columns that supported its roof.

Next to the Apadana was the Throne Hall, the second largest building at Persepolis, where the king received nobles, dignitaries, and envoys bearing tribute. An enormous throne room, 70 by 70 m (230 by 230 ft), occupied the central portion of the Throne Hall. It is also known as the Hundred-Column Hall after the 100 pillars that supported its roof. Eight stone doorways led into the throne room. Carvings on the sides of the doorway depict the king on his throne and the king in combat with demons. The Throne Room was begun by Xerxes and completed by Artaxerxes I.