Climate change is having an impact in the vast and remote region of Yakutia in Siberia which, in winter at least, is still the coldest place on earth. Bridget Kendall reports.
There cannot be many foreigners who make it as far as Yakutia's top tourist attraction, the Ice Kingdom.
The way in is through an unassuming wooden door cut into the hillside, just like the entrance to Bilbo Baggin's hobbit home in The Lord of the Rings.
You pass into a dark hallway strewn with straw and blocks of ice, and enter another world.
White crystals sparkle. A tunnel shimmers blue as far as the eye can see. In padded silver capes, guides usher us through caverns carved with ice sculptures.
One houses the ivory tusks of a mammoth. In another, a young man draped in furs sits on an icy throne. "The Lord of the Cold," our guide tells us.
"How long have you been here?" I ask. "Eternity," he answers with stoic humour.
In fact, no-one could last long in these icy caverns without a break.
Just one and a half metres from the surface, the ground is permanently frozen at -10C.
Yakutia is home to the permafrost. In midwinter, outside temperatures make it the coldest place on earth - an unbelievable -70C.
Luckily September is still fleetingly autumn. The trees seem to fade from green to yellow overnight.
In just four days the temperature drops noticeably. The local paper worries that not all heating plants are yet fully repaired and supplied with fuel. The first frosts, it says, will come in days.
Evidence of extreme temperatures is visible everywhere. Newer buildings perch on concrete permafrost stilts.
The asphalt on the buckled roads erupts into cracks and bumps, while lagged heating pipes snake over head. Untidy spaghetti wires loop from one high-rise to another. You can not bury power lines and pipes in the permafrost.
There are also telling signs of what looks like global warming. This July in the underground Ice Kingdom the temperature rose to a dangerously warm -7C. On the surface winter frosts rarely get harsher than -50C.
"Not that it makes much difference when it is that cold," says the republic's prime minister, trying to brush off warnings of erosion to the permafrost. "Who is to say global warming is really happening?"
Fair enough. If you spend 10 months of the year struggling to survive in deep refrigeration, dire predictions about global warming probably do seem overblown.
But Yakutia is also frozen in another way, trapped in a time warp of a lost Soviet age. It is almost charming.
In the capital, Yakutsk, Lenin still towers over the main square.
Rooftop slogans and murals have replaced eulogies to Soviet communism with "friendship through sport" and "the glory of war veterans".
The cruise ship we boarded on the river Lena is called Demyan Bedny, after a minor and rather bad Soviet poet, whose book and those of several other now forgotten mediocre writers are proudly displayed in the ship's library.
The Siberian Lena river is the 10th longest river in the world
"I am often asked why we are so poor and backward when we are sitting on such wealth," says the prime minister. Yakutia yields over 90% of Russia's diamonds, as well as gold and numerous other precious metals, and increasingly oil and gas.
Yet apart from one or two showy hotels, much of the capital looks like a village. Rickety wooden houses are squeezed in between modern tower blocks.
Side streets are little more than muddy tracks. There is a constant problem of houses being burnt down, according to the local paper, and packs of wild dogs that attack passers-by, even in the town centre. Marshy swamps and scrubland give the place an abandoned feel.
Isolation and lack of transport is half the problem. There is not even a railway in Yakutsk. There are plans to put one in, and build new roads and pipelines from the mines and oil fields.
But this year's economic crisis has not helped. It led to a collapse in the price of diamonds.
Moscow had to step in and help out.
Back on the boat Demyan Bedny, I find a safety notice in my cabin.
"If you fall in, whatever you do, DO NOT SWIM!" it says sternly. Hypothermia from the Lena river's icy current is the main risk. Apparently I must tread water until the crew come to rescue me.
As we leave the river port, we pass rusting hulks and crumbling docks.
But as we float up this wide Siberian river past startlingly beautiful cliffs, in a region almost the size of India, I cannot help thinking of the mineral wealth hidden beneath its frosty crust.
Asia, we hear so often, is the powerhouse of the future. For Russia, surely it is the wealth of still untapped resources here, in Eastern Siberia, that will guarantee future clout... not the nuclear missiles of yesteryear.
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