Exploring the grandiose buildings and industrial infrastructure left over from the USSR is a popular pastime for some young people - but not the faint-hearted.

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Known as urban exploration, the hobby involves climbing high-rise buildings, towers and bridges, or going deep underground. Russia's vast territory is dotted with industrial sites, some of which are unused and empty. But Vadim Makhorov was commissioned to take these pictures inside a water pipe by the owners of this functioning power plant in the east of the country.

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Many urban explorers are skilled photographers who take striking images. "Who needs words when you've got stars in the sky?" asks Vitaly Raskalov, who took this picture of Kirill Vselensky clinging to a Soviet-era red star which adorns a building in Moscow. But the dangers are obvious. It's not a hobby that should be encouraged. Many of the explorers do not even take the precaution of wearing a helmet. At least one is reported to have died.

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General Kosmosa's picture shows an urban explorer taking a break on top of Kiev's South Bridge over the River Dnieper, which is the tallest in Ukraine at 135m (443ft).

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Taking this picture was dangerous in more ways than one. The clock that Kirill Vselensky's face is emerging from is located across the street from the main KGB building in Minsk, Belarus.

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Under Russian law, trespassing on private property is punishable by a small fine, but entering abandoned and unguarded buildings is usually legal.

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"What appeals to me the most is the ambience of lost places," says Sam Namos, who took the picture below of an explorer known as Vanh1to, atop a huge satellite dish. "The process of looking for them is breathtaking, too. If you're serious about it, there is so much you can learn about your own country, so many mysteries you can discover."

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"Some say if you see one power station, you've seen them all, but I disagree," says Vadim Makhorov. "I've done photo-shoots at many power plants, and I manage to find something new and interesting every time."

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"Urban exploration photography shows our cities from the inside," says Olena Zinchenko, who helped to organise an exhibition in Kiev last year. "These pictures are alive because they reveal the city from a completely different perspective which few have the privilege of seeing." They're important, she says, because they tell the story of industrial decline in the the former Soviet Union.

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"This is probably my best find, a gypsum mine in eastern Ukraine. An inconspicuous door led to an underground city with its own traffic, street signs and 20-metre-tall caves," says Yaroslav Segeda.