Description : Persepolis was the ceremonial capital of the Achaemenid Empire ( 550–330 BC ). Persepolis is situated 70 km north east of city of Shiraz in Fars Province in 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 great palaces Gated hall the main imperial Treasury and its surroundings. These were completed during the reign of his son, King Xerxes the Great. Further construction of the buildings on the terrace continued until the downfall of the Achaemenid dynasty. Persepolis is near the small river Pulvar which flows into the river Kur. The site includes a 125,000 square metre terrace partly artificially constructed and partly cut out of a mountain with its east side leaning on Kuh-e Rahmet . The other three sides are formed by retaining walls which vary in height with the slope of the ground. Darius ordered the construction of the Apadana Palace and the Council Hall ( the Tripylon or three-13 metres on the west side a double stair ). From there it gently slopes to the top. To create the level terrace depressions were filled with soil and heavy rocks which were joined together with metal clips. Around 519 BC, construction of a broad stairway was begun. The stairway was planned to be the main entrance to the terrace 20 metres above the ground. The dual stairway, known as the Persepolitan stairway was built in symmetrically on the western side of the Great Wall. The 111 steps were 6.9 meters wide with treads of 31 centimeters and rises of 10 centimeters. Originally, the steps were believed to have been constructed to allow for nobles and royalty to ascend by horseback. New theories suggest that the shallow risers allowed visiting dignitaries to maintain a regal appearance while ascending. The top of the stairways led to a small yard in the north-eastern side of the terrace opposite the Gate of Nations Grey limestone was the main building material used in Persepolis. After natural rock had been leveled and the depressions filled in the terrace was prepared. Major tunnels for sewage were dug underground through the rock. A large elevated water storage tank was carved at the eastern foot of the mountain. The uneven plan of the terrace including the foundation acted like a castle whose angled walls enabled its defenders to target any section of the external front.