Why would anyone risk his life to venture here to the Wild West of Laos's northern Xieng Khouang province ? To see the most extraordinary relics of a vanished civilisation - fields of weathered stones that have been described as the Stonehenge or the pyramids of south-east Asia.
Scattered around the hilltops, under the shade of wild guava and crocodile trees, are thousands of enormous lichen-covered urns carved out of solid sandstone - some upright, some canted on their sides, split by encroaching tree-roots. The largest are almost three metres tall and weigh an estimated six tonnes .
Although it is 70 years since a French archeologist named Madelaine Colani established a study institute here and first brought the jars to the attention of the West with her book Les Megaliths du Haut Laos (The Megaliths of Upper Laos) no-one yet has any real idea who made them, or how, or what they were for - or what became of that ancient civilization.
In part it is the remoteness of the site. No sealed roads connect the honky-tonk provincial capital of Phonsavan with the rest of Laos - you have to take your chances on a clapped-out Lao Airlines AR72 with broken seats and the windows so scrazed you can barely peer through them. We flew up with three Japanese mine-clearers also headed for the Plain of Jars.
As you fly in you get your second clue as to why the world's most eminent historians are not queueing up to solve the mystery of the megaliths. The hills have been denuded of their jungle cover, and now resemble a golf-links pocked with thousands of bunkers.
This is the dreadful legacy of the greatest aerial bombardment in the history of warfare. The Ho Chi Minh Trail, down which the Vietcong moved arms and men and supplies for their war with the Americans and their allies, ran through Xieng Khouang province and was subject to bombing on a scarcely-conceivable scale for more than a decade.
That night, after a spicy stir-fry of hedgehog and a glass of mushroom-flavoured lao-lao (the local rice-wine) at the Phetrasy family's inn we watch a video of a Discovery/Times documentary, The Ravens -- Secret War In Laos, which tells the story.
Between 1964 and 1973, the Americans dropped more explosives on Laos than they did during the whole of World War II - two million tonnes, which is the equivalent of one B52 mission every eight minutes for nearly a decade, or half a tonne of explosives for every Laotian.
Many of these were cluster bombs which opened in midair, releasing 670 bomblets, each containing a charge of explosives and 300 ballbearings. About one third of these failed to explode - scattered over northern Laos are millions of these deadly "bombies" which continue to maim and kill at least one Laotian a week, many of them children.
Thanks to international mine-clearing teams, particularly the Manchester-based Mines Advisory Group (MAG), about 200,000 pieces of UXO (local slang for unexploded ordinance) are being destroyed a year. But it will still be decades before huge tracts of the countryside, including areas of the Plain of Jars, can be declared safe.
Lan Phetrasy, who is 29, and his father Sousath, a war veteran who learned his English from a downed American airman, have been largely responsible for opening up the Plain of Jars since the war, although still only a trickle of 150 or so intrepid tourists make their way up here every week.
Three "fields" of jars - actually rolling hillsides, pocked with bomb-craters and slashed with the slit-trenches and the fox-holes in which the Pathet Lao soldiers hid while the B52s thundered overhead - have now been opened up to the public.
But many more sites are waiting to be rediscovered. Madelaine Colani located about 10,000 of these megaliths - but unfortunately she gave directions from villages that have been obliterated from the map by the war. Twenty entire villages have disappeared.
Only about 3000 jars have been relocated - the desperately-poor country cannot afford the satellite survey that would be needed to find the rest, and cannot protect existing sites from vandalism and theft - the CIA even tried to airlift one back to Langley, Virginia, by helicopter but gave up when the steel hawser began to saw through it.
Local legend has it that a sixth century Lao warrior, Khun Jeuam, had the jars constructed to brew rice wine to celebrate a military victory. But less romantic scientists believe they were the work of a civilization that migrated over the millennia from northern India through south-east Asia to Indonesia. Similar urns have been found in Assam and in the Sulawesi Islands.
They appear to have been hollowed out by hand, using flint and bronze tools, which would date the urns back as far as 2000BC, making them older than the Great Pyramid of Giza in Egypt or the Xian terracotta warriors in China.
What were they for ? Although various artifacts - carnelian beads, bronze bracelets, ceramic pots - have been found nearby, there are no signs of human remains in the pots. It is likely that they were used for what are called "secondary burial" rituals, in which the remains are removed after decomposition for cremation or burial elsewhere.
However, the sites remain sacred to the local villagers. Until quite recent historical times - a couple of hundred years ago - Phetrousy says there were annual ceremonies where buffalo were slaughtered as an offering to whatever unknown animist gods they worshipped.
And somewhere deep in the woods, at a secret location, Lan Phetrousy says he knows of a dozen urns which are still sealed with their stone lids. They may hold the key to the mystery of the megaliths - but this will have to wait for a serious scholar with the time and the money to mount a proper scientific investigation.
In the meantime, tourists are welcome to wander the Plain of Jars and let their imagination run free. And, if archeology palls, there are plenty of other things to do in this remote corner of the world.
Many villagers grow silk-worms and weave intricately-patterned scarves which they are eager to sell for a few dollars. At Bau Noi, you can bathe in sulphurous hot springs on the banks of a pretty creek. The local cuisine is cheap and spicy, Thai food on steroids, and includes lots of "wild food" like fruit-bats, badger, termite eggs, and swallows which they net when the birds fly in for dust baths in the bomb craters.
Most of the villages hereabouts survive on subsistence agriculture, and they have ingeniously taken advantage of the hundreds of thousands of tonnes of metal that fell from the skies - literally beating swords into ploughshares. Shops in Phonsavan sell ashtrays made of rocket-propelled grenade casings.
At one Khmer village not far from the Plain of Jars bomb casings support rice granaries, form fences and are used for pig-troughs and planter-boxes. The local blacksmith has made his forge out of war debris - the firebox is a Russian truck fuel-tank, the bellows a flare casing, and the anvil where he beats out knives and hoe-heads is the nose-cone of a 1000lb bomb.
Nearby Tham Piu is probably the most somber war memorial in all of Laos. Here, in 1968, a US fighter-plane fired a rocket into a cave suspected of being a Vietcong supply dump where hundreds of local villagers had taken shelter - a makeshift alter with a human skull on it marks the spot where 374 men, women and children were incinerated.
Phonsavan is not for everyone. The raw aftermath of war is everywhere. But the people are welcoming - Australians today are known more for the roads, bridges and schools they are building here, than their participation in the war.
And the Plain of Jars is, quite simply, one of the world's great undiscovered archeological treasures.
Lao Airlines has two flights a day between the capital Vientiane and Xieng Khouang, the airport for the Plain of Jars. The return fare is $US96.
The Vansana is the best hotel in Phonsavan - it's modern, comfortable, air-conditioned, and has a bar and restaurant. A double room is $US40 a night, including breakfast and airport transfers. http://vansana.laodpr.com. The Maly Hotel/Restaurant is fun and funky and costs $8-$30 for a room - www.malyht.laotel.com.
Only the hotels take credit cards, and there are no reliable money-changing facilities in Phonsavan. Take cash -- US dollars are best.
Be sensible about what you eat and drink - use only bottled water, avoid salads and be careful with fruit. Have hepatitis A shots before leaving, and take anti-malaria pills; use spray and mosquito nets. Pay attention to land-mine warnings and do not stray off the beaten paths.
Ben HillsTo be published by the Sydney Morning Herald
Photography: by Mayu Kanamori