Difficulty: Summiteer (Level 3)
Conservationists at Persepolis, Iran’s most iconic ancient site, are waging a battle against an unlikely enemy.
They are fighting lichens, organisms that grow on surfaces like stone and can slowly break them down over time. These lichens threaten to destroy the monuments.
Built in the 6th century BC by Darius I, Persepolis has withstood destruction, looting, earthquakes, fires and harsh weather. It has been a Unesco World Heritage site since 1979. Persepolis has giant sculptures and stone reliefs of ancient Persian kings, nobles and gods.
But these have suffered from lichen, a combination of an algae and a fungus.
“This is the most serious problem, especially for carvings on stones,” said Shahram Rahbar, a conservationist at the ancient site.
Answer: lichens
