Updated

The European Union and the World Bank are in discussions to help pay for the rebuilding of cultural heritage destroyed by the Islamic State group in Iraq.

The extremists, now in retreat, once held hundreds of sites small and large across Iraq.

Francesco Bandarin, assistant director-general at UNESCO, said the U.N.'s cultural body and Iraqi officials are discussing how to pay to rebuild the sites, which include some of the earliest cities of humankind.

Bandarin said the reconstruction and restoration effort was likely to take not years, but decades.

HATRA

Islamic State extremists bulldozed the ruins of this 2,000-year-old city, a day after pillaging Nimrud. A complex of temples south of Mosul, Hatra's thick walls resisted two Roman invasions in the 2nd century A.D., only to crumble under Islamic State's explosives. The militants are still in the area, which had been a well preserved complex of temples south of Mosul and a UNESCO World Heritage site.

NIMRUD

Nearly 3,000 years ago, this city ruled the Middle East. Islamic State blew apart the remains of its palaces and temples. The statues of winged bulls that once guarded the site were hacked to bits and piled high. Its towering ziggurat, or step pyramid, was bulldozed in a final frenzy of destruction as Iraqi forces closed in last fall. Iraqi officials estimate it's around 70 percent destroyed.

ST. ELIJAH'S MONASTERY

A 1,400-year-old structure on the outskirts of Mosul that survived assaults by nature and man for centuries, St. Elijah's was razed to the ground in August 2014. The monastery, called Dair Mar Elia, is named for the Assyrian Christian monk — St. Elijah — who built it between 582 and 590 A.C. It was a holy site for Iraqi Christians for centuries, part of the Mideast's Chaldean Catholic community. Only track marks remain where the monastery once stood, and the site near Mosul's airport remains under tenuous Islamic State control.

ASHUR

The 3rd millennium ancient city of Ashur in Shirqat was the first capital for Assyrian Empire between 14th to 9th centuries BC. The militants claimed that they had destroyed some of its ruins, but they didn't release a video as they did with other archaeological sites. Islamic State no longer controls the site, but it is not yet secure enough for archaeological experts to evaluate.

MOSUL MUSEUM

In February 2015, extremist websites showed footage of Islamic State militants with sledgehammers destroying ancient artifacts at the museum in Mosul which they referred to as idols. Iraqi archaeologists say the extremists looted the museum before trashing it. The museum is just across the river on Mosul's west bank, practically within reach of Iraqi forces in the city.