Heaven meets hell where blue hills lining Mongolia's vast grasslands, untouched for millions of years, have been turned into giant slag heaps.
Multi-storey floating dredgers scoop up the beds of newly diverted rivers and, with metallic rumblings straight out of a sci-fi film, crunch and separate the gold-bearing deposits from the debris they disgorge 24 hours a day.
Vast floodplains, above which at night the Milky Way stretches across the sky, are being turned upside down and areas just as big await a similar fate.
Nearby, goldrush towns are rising from the dirt, turning the central part of the land of Genghis Khan into a squalid Wild West.
It is all legal.
But at night, the dredgers are followed by the ninjas -- illegal miners named after the green, turtle-shell-like pans they carry on their backs -- who sift the droppings under cover of darkness and pan them for the gold the dredgers have missed.
The only sign of the ninjas the next morning is the dozens of discarded batteries from their torches.
Mongolia, once the center of one of the world's greatest empires, has gold in them thar hills, and foreign companies have been quick to grab a piece of the action.
Some multinationals have tried to clean up the mess they leave behind, but others have done nothing. As for the ninjas, they are doing irreparable damage -- to the environment, to themselves and to the herders living nearby in circular, white tents called "yurts" in Russian and gers in Mongolian.
In some places the ninjas simply dig 20m holes in the ground, or sift disgorged material left by the dredgers or pan rivers, using a system of secret flashes and calls at night to warn the others of danger or of an approaching official.
Elsewhere they use poisonous mercury to absorb the gold and then boil the mixture, evaporating the mercury, to get at the gold. In some gers, the apparatus sits next to the kitchen stove.
"We have found herders with five to six times the safety limit of mercury in their urine," said D. Jargalsaikhan, chairman of the Mineral Resources Authority of Mongolia.
"The damage the ninjas are doing is a major problem. Also, about 30 percent of small [legal] gold miners do not care about the environment."
Nomadic livestock herding of sheep, goats, horses, cattle, yaks and camels, constitutes the core of Mongolia's economy and represents the basis of the nation's cultural traditions.
About 60 percent of the country is covered by grassland while the Gobi desert envelops the south.
The ninjas are herders who lost everything in three years of devastating "zuds," or disasters. Some turned to illegal mining just to survive. Some are making it rich.
Other ninjas are relatives of legal miners holed up in such gold-rush towns as Ogoomor Baga, with its delapidated shacks and central, non-stop disco. Some are legal miners working overtime.
On the central steppe of Zamaar, the ninjas live brazenly in camps of hundreds of gers and traditional pitched tents.
"We can't go in there," said a Mongolian geologist, watching one such camp after he had navigated the mostly dirt roads for five hours from the capital Ulan Bator. "There may be drunks, bad people. We don't want to start a fight."
All was quiet. In the camps there are shop gers, satellite television gers, pool-playing gers and even girlie-bar gers. All surrounded by treacherous holes in the earth, old mines that give way and kill all too often.