UNESCO has said the historic city of Palymra in Syria must be protected.
The call comes after intense fighting between forces loyal to President Assad and ISIL militants already caused some damage.
The militants reportedly withdrew from the site on Sunday after seizing it a day earlier.
Irina Bolkova is from the United Nations organisation which protects world heritage sites.
She said: “Palmyra is an unbelievable monument in the middle of the desert. It is a place where we see different cultures. From Rome, Byzantine and Persia, Greece and Islam … We can not permit that Palmyra will be destroyed.”
Palmyra was founded in around 2000 BC as a caravan stop for travelers crossing the Syrian desert.
By the third century AD it was a prosperous metropolis and is mentioned in many ancient texts including the Hebrew Bible.
ISIL has already deliberately destroyed many ancient relics in Iraq in a bid to crush what it called non-Islamic ideas.
The city is strategically important because it sits at a crossroads linking it to the cities of Homs and Damascus.