Israel opened its border to Gaza for the first time in months, to allow rebuilding supplies in to the Palestinian territory in the wake of the summer conflict.
On a rare visit to Gaza, the UN's Secretary General Ban Ki-moon said the destruction he witnessed was "beyond description," adding that it was worse than the devastation he witnessed after the 2008-2009 war.
Much of Gaza's infrastructure was destroyed during 50 days of fighting that saw Israel pound the coastal enclave with air strikes and a ground invasion in response to a series of rocket attacks.
The territory's only power plant was left inoperable after apparent Israeli attacks, resulting in power outages lasting up to 18 hours per day. Attacks also damaged or destroyed two major sewage treatment plants, as well as 20%-30% of Gaza's water and sewage networks, leaving half a million Palestinians without running water.
Israel has said it was allowing 600 tonnes of cement, 50 truckloads of gravel and 10 truckloads of steel in to Gaza to for the purpose of rebuilding homes and public institutions. The transfers would be monitored by the UN and the Palestinian Authority.
Israel and Egypt had enforced a strict economic blockade on Gaza in the months before the fighting, in addition to the seven-year partial blockade that Israel established in 2007.
Israel's government has come under fierce pressure from human rights groups to lift the blockade in upcoming peace negotiations with Palestinian leaders.
UN chief Ban visited a number of sites damaged in the war, which left more than 2,100 Palestinians dead, the vast majority of whom were civilians. Israel lost 67 soldiers during the fighting, as well as six civilians.
"I am here with a heavy heart," Ban told reporters. "The destruction which I have seen coming here is beyond description."
At an international donor conference in Cairo on Sunday, attendees pledged $5.4bn (£3.4bn) to support Gaza's reconstruction, although much of the funds will be used to support the Palestinian budget.