Tehran, 8 Jan. (Iranian Cultural Heritage News Agency) -- The steps to the Apadana entrance and the doorway to the 2500-year-old palaces in Persepolis have been eroded by 1 to 2 mm.

The erosion in the world heritage site of Persepolis has made the experts so anxious that they have begun a special study of the Achaemenid capital to find out about the reasons of the erosion of bas relieves and the other parts of this ancient site.

“According to our studies, the traffic of visitors of which the number in some days goes up to 20 thousand is one of the reasons for the erosion of the floor of the steps and doorways in Persepolis”, Hassan Rahsaz, a technician in Persepolis historical complex, told CHN.

Given the extensive erosion, the experts in Parse and Pasargadae research foundation have looked for suitable ways in the last few years to prevent more damage in this site. In a pilot project, a part of the eastern stairway to one of the palaces is covered with timber, and 882 meters of the floor of the steps and doorways will be covered with Indian redwood, said Rahsaz.

There will be a space between the steps and the floor timber, so that the air is circulated and dampness is prevented.

Founded by Darius I in 518 B.C., Persepolis was the capital of the Achaemenid Empire. It was built on an immense half-artificial, half-natural terrace, where the king of kings created an impressive palace complex inspired by Mesopotamian models. The importance and quality of the monumental ruins make it a unique archaeological site.