Rebuilding homes and infrastructure after Israel’s 15-month war on Gaza could take 40 years and cost more than $80 billion, aid agencies said on Friday.

The war has transformed the enclave into a rubble-strewn wasteland with blackened shells of buildings and mounds of debris. Major roads have been plowed up. Critical water and electricity infrastructure is in ruins. Most hospitals no longer function.

The full extent of the damage will be known only when the fighting ends on Sunday and inspectors have full access. The most heavily destroyed part of Gaza, in the north, has been sealed off and largely depopulated by Israeli forces in an operation that began last October.

Using satellite data, the UN estimates that 70 percent of structures in Gaza have been damaged or destroyed, including over 245,000 homes.

Before anything can be rebuilt, the rubble must be removed — a staggering task in itself.

The war has littered Gaza with over 50 million tonnes of rubble, about 12 times the size of the Great Pyramid of Giza. With over 100 trucks working full time, it would take 15 years to clear.

“I can’t think of any parallel, in terms of the severity of damage, for an enclave or a country or a people,” said Corey Scher of the Shelter Cluster, an international coalition of aid providers led by the Norwegian Refugee Council.

The first target for aid is the health sector, with more than 80 percent of Gaza’s health facilities damaged or destroyed.

The World Health Organization said on Friday it would start by bringing prefabricated hospitals into the enclave and medically evacuating over 12,000 patients, a third of them children.