On the Kazakh-Uzbek border, surrounded by miles of toxic desert, lies an island. Or at least, something that used to be an island.

Vozrozhdeniya was once home to a vibrant fishing village fringed by turquoise lagoons, back when the Aral Sea was the fourth-largest in the world and abundant with fish.

But after years of abuse by the Soviets, the waters have receded and the sea has turned to dust; the rivers that fed it were diverted to irrigate cotton fields. Today, a layer of salty sand, riddled with carcinogenic pesticides, is all that remains of the ancient oasis.

This is a place where the mercury regularly hits 60C (140F) in the sandy soil, and where the only signs of life are the skeletons of desiccated trees and camels shading under giant, stranded boats.

Now Vozrozhdeniya has swallowed up so much of the sea that it’s swelled to 10 times its original size, and is connected to the mainland by a peninsula. But it is thanks to another Soviet project that it is one of the deadliest places on the planet.

From the 1970s, the island has been implicated in a number of sinister incidents. In 1971, a young scientist fell ill after a research vessel, the Lev Berg, strayed into a brownish haze. Days later, she was diagnosed with smallpox. Mysteriously, she had already been vaccinated against the disease. Though she recovered, the outbreak went on to infect a further nine people back in her hometown, three of whom died. One of these was her younger brother.

A year later, the corpses of two missing fishermen were found nearby, drifting in their boat. It’s thought that they had caught the plague. Not long afterwards, locals started landing whole nets of dead fish. No one knows why. Then in May 1988, 50,000 saiga antelope which had been grazing on a nearby steppe dropped dead – in the space of an hour.

The island’s secrets have endured, partly because it isn’t the kind of place where you can just turn up. Since Vozrozhdeniya was abandoned in the 1990s, there have only been a handful of expeditions. Nick Middleton, a journalist and geographer from Oxford University, filmed a documentary there back in 2005. “I was aware of what went on, so we got hold of a guy who used to work for the British military and he came to give the crew a briefing about the sorts of things we might find,” he says.

“He scared the pants off me, to be honest.”