Facebook is being used by networks of traffickers to buy and sell looted antiquities, the BBC has learned.
Private groups also discuss how to illegally excavate ancient tombs, according to research by academics.
Facebook says it has removed 49 groups following the BBC's investigation.
The BBC has also seen evidence that antiquities are still being smuggled from Iraq and Syria into Turkey, despite a police clampdown and the retreat of the Islamic State group.
‘Facebook's watch'
Roman mosaics still in the ground in Syria are being offered for sale on Facebook pages shown to the BBC by Prof Amr al-Azm, an archaeologist who has had to leave Syria and now works at Shawnee State University in Ohio.
On the rooftop terrace of a restaurant overlooking the Bosphorus in the Turkish city of Istanbul, he points to a Facebook photograph of a sculpture which a user in northern Syria claims is from the ancient site of Palmyra, looted and damaged by Islamic State.
