Syria's six-year conflict has caused losses of $226 billion (Dh830bn) to its economy, according to estimates published by the World Bank on Monday.
The report came as the UN envoy to Syria Staffan de Mistura opened the seventh round of indirect talks in Geneva between Syrian government representatives and opposition leaders to try to wind down the civil war.
The war has killed over 320,000 people and displaced more than half the country's population since it began in March 2011, but the destruction ran much deeper than death tolls or infrastructure damage, the World Bank said.
"The number of casualties is devastating, but the war is also destroying the institutions and systems that societies need to function, and repairing them will be a greater challenge than rebuilding infrastructures," World Bank vice president for the Middle East and North Africa Hafez Ghanem said.
The World Bank report found that cumulative GDP losses since Syria's conflict erupted "have been estimated at $226bn, about four times the Syrian GDP in 2010."
It estimated that the conflict had damaged or destroyed 27 per cent of Syria's housing stock and about half the country's medical and educational facilities.
Those calculations were based on cross-checked satellite imagery of certain cities and areas and extrapolated based on a conflict intensity model.
The World Bank also found an average of 538,000 jobs had been lost annually between 2010 and 2015. It said more than three in four Syrians of working age — or about nine million people — were neither employed nor enrolled in any form of school or training.
"The long-term consequences of this inactivity will be a collective loss of human capital leading to a shortage of skills in Syria," it said.
During talks in Geneva, Mr de Mistura said agreements to de-escalate the fighting in Syria could simplify the conflict and lead to a phase of stabilising the country, but such deals must be an interim measure and avoid partition.
The start of the talks in Geneva coincided with the first full day of a ceasefire for southern Syria that was brokered last week by the US, Russia and Jordan.
Speaking at the start of five days of peace talks, Mr de Mistura said there were discussions in Amman to monitor the implementation of a US-Russian brokered ceasefire for south-west Syria.
"The agreement is basically broadly holding, quite well. In all agreements there is a period of adjustment, we are watching very carefully," Mr de Mistura said. "But we can say we believe it has fairly good chances of working out."
The Geneva talks are expected to last through the week.
The UN envoy will be shuttling between the two sides, which have so far only faced each other in ceremonial meetings that have been short on substance. Mr de Mistura was first to meet with representatives from Syrian president Bashar Al Assad's government on Monday, before a meeting later with opposition representatives.
The UN-led diplomatic efforts seek partly to ensure humanitarian aid deliveries to Syria and plan for the day after the war is over.
The Syrian opposition is determined to achieve a political transition in Damascus, while Mr Al Assad's government insists the talks should prioritise "the war on terror".