BBC environment analyst Roger Harrabin reports on how a push toward electric scooters in one Chinese city could be a bellwether for a global revolution.
The incredible limestone karst pinnacles of Guilin are indeed a wonder of the planet.
I am still shaking my head in disbelief at this freak of nature.
But the world may owe another debt to this remarkable city by helping to popularise the electric scooter.
Battery-powered motor scooters are popping up in cities right across China. But in Guilin, they have been given an extra boost by the decision of the local authority to stop issuing licences for conventional motorbikes, which were sullying the city's green reputation with their pollution and noise.
As a result, most of the powered two-wheelers in Guilin are now silently electric - sometimes alarmingly so, as I discovered while turning to cross the road.
Air pollution has been reduced at a two-stroke, and there's also a bonus cut in greenhouse gases.
As the UK government's chief energy scientist David MacKay shows in his recent book, it's better to run vehicles on electricity than petrol even if the power is generated by coal.
That's because electric motors are so much more efficient than internal combustion engines.
A simple change in regulations in just one large city can make a small difference in terms of orders and production for a clean technology like this. As production volumes increase, prices come tumbling down.
Cycle swap
If locals in Guilin are determined enough to buy a petrol scooter, they can still scam a licence from a friend in the county area. But now most wannabe two-wheel speedsters are choosing electric scooters because they are cheaper to buy and to run.
My guide in the city Joy Hu told me he bought his scooter because it was good for the environment, easy to ride, and cheaper to buy and to run than a petrol model.
But he confessed that for almost all other riders, the price was the only significant factor. He said you could now buy scooters in the town for £450-£500. Charging them overnight gives you enough power to do anything you needed to do in the day for much less than a tank of petrol.
China's population is so vast and demand is so huge that it is surely just a matter of time before the prices for electric scooters are driven so low that they are commonplace around the world.
A couple of caveats though: the Chinese government is not quite as omnipotent as it often appears from abroad.
The provinces have enormous influence and politicians do all they can to protect their local industries regardless of the wishes of the state. So we can expect that the areas that manufacture dirty, noisy old bikes will try to find a way to keep them for a while.
The second caveat goes deeper. Greens may enthuse about the rise of electric vehicles but Wan Li , my interpreter in Yangshuo near Guilin, told me almost all of the scooters in the region were being driven by people who had given up their pedal cycles.
This has implications for health policy as the Chinese increasingly eat a more Western-style, high-fat diet.
It also has emissions consequences if low-pollution electric bikes become so cheap that they replace not just high-pollution petrol motorbikes but zero-pollution bicycles as well.
"In 30-40 years' time I don't think anyone will ride a bicycle in China," opined Mr Li. "Everyone will want to have a car."
Of course, his prediction may be wrong: in developed countries some people who can afford a car still choose to cycle. And there are other factors - like lack of space - which will restrict limitless ambition for mobility.
But it is a sobering thought that the world needs to generate enough energy and create enough pollution-absorption room in the atmosphere to cope not just with current demand, but with the future demands of nine billion of us.
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