A year ago, it was forbidding desert terrain dotted with empty tents whipped by a scorching wind.
"No-one would want to live here," the UN's Andrew Harper admitted bluntly to the small gathering of Jordanian officials, foreign diplomats and aid workers who assembled under an awning for the opening of Jordan's first official Syrian refugee camp at Zaatari.
Now it is Jordan's fourth largest city.
And nobody wants to live there.
"On that day it opened we simply had no idea it would grow so big, so fast," one UN official told me on a recent visit to the camp, which has mushroomed into a vast crowded canvas dissected - with growing difficulty - by orderly grids drawn up by the world's aid agencies.
Few expected Syria's war to drag on so long, cause so much suffering, cost so many lives. The death toll is now 100,000 and counting.
Last year, when we reported on the opening of Zaatari camp, a Syrian woman living in a modest dwelling in a nearby town declared to us: "I would prefer to die in Syria than live in that desert".
A few weeks ago in Zaatari, I did see long queues of families waiting in the baking heat, hoping to find seats on buses to take them back across the nearby border in the dark of night. The demand for transport is now outstripping the supply.
But many more have no choice but to stay. Their homes in Syria are destroyed, their neighbourhoods too dangerous, after more than two years of a worsening war. More than 120,000 Syrians now call Zaatari home, making it the world's second-largest refugee camp.
But it's rapidly taking on the trappings of a city. There are plans for water and electricity meters, UNICEF is building more schools, narrow lanes drawn in the sand are now called streets.
There's even a dusty avenue of corrugated tin shops dubbed the "Champs Elysees", where you can buy sweet ice-cream or sizzling kebabs, get your laundry done, buy a wedding dress - if you can afford it.
Most are almost completely dependent on assistance. The arithmetic of this aid is staggering. The UN's World Food Programme, along with Save the Children, now distributes half a million portions of bread every day along with other rations. There were 92 million loaves for Zaatari in the past year.
But food aid will soon become vouchers, and tents are being replaced by trailers, fast becoming the accommodation of choice although there are not enough to go around.
And, like any fast-growing city, Zaatari has its security concerns including criminal gangs and local vendettas. The day I visited, a Jordanian police officer was in the camp discussing plans for 24-hour policing.
For a long time, Syrians insisted they did not want, and did not need, that kind of security since they didn't expect to stay in Zaatari for long.
But even in this makeshift city beyond Syria's borders, the Syrian government's victory over opposition forces in the town of Qusair last month had a psychological impact.
"The next day, local representatives came to us and said they wanted to discuss arrangements for the camp," said one aid official. "They realised they may not be going back as soon as they thought."
'Minister of electricity'
The UN's Killian Kleinschmidt, who runs Zaatari for the UN's High Commissioner for Refugees, now calls himself the mayor. He told me how he sits down with everyone from visiting dignitaries to local self-appointed street representatives.
There is even a self-styled "minister of electricity" helping to sort the tangle of illicit wires exploited by boot-leggers.
One earnest young boy clutching a pile of new school books flagged down our vehicle with an urgent plea - he didn't have a notebook to start doing his homework. A Unicef officer quickly found one and he happily disappeared with his friends into a warren of tents.
Even the children dream of a better day. When they were asked to paint happy scenes on the bare walls of their school trailers, they drew lush green landscapes with story-book houses that looked like Switzerland.
For their parents, their refuge has troubling echoes of the exodus of Palestinian refugees in the 1948 and 1967 wars. Palestinians also said then that they "weren't here for long. But their camps are now indistinguishable from other crowded neighbourhoods in Jordan and neighbouring countries.
This latest influx is also putting significant strain on all of Syria's neighbours who have taken in about 1.6 million refugees. The UN says 6,000 more cross one border or another every day. Jordanians, with their own financial woes, worry about rising prices and pressure on schools and jobs, from the estimated 400,000 displaced Syrians who live outside the Zaatari camp.
Nobody wanted to live in Zaatari. And now nobody can say, with any certainty, how long they will stay, and how many more will come.