Here’s what you’ll learn when you read this story:

• Vozrozhdeniya Island, located in the Aral Sea along the Uzbekistan-Kazakhstan border, played a large part in the Soviet Union’s bioweapons program.
• For decades, 150 scientists, technicians, and soldiers tested weapons that used plague, smallpox, and even anthrax—with several deadly accidents.
• Although it was abandoned in the early 1990s, the U.S. and Uzbekistan didn’t officially decontaminate the site 2002, finally consigning its deadly weapons to history.

In the mid-20th century, the small town of Kantubek—nestled on Vozrozhdeniya Island in the Aral Sea—was much like any other. Home to some 1,500 people, the small outpost along the remote Uzbekistan-Kazakhstan border had its own school, a few shops, and even a post office. However, behind this bucolic facade, Kantubek was hiding a deadly secret. Alongside those emblems of small-town life were research facilities, animal pens, rifle ranges, barracks, and open-air testing sites. During this period of history, Kantubek went by another name: Aralsk-7, the heart of the Soviet Union’s bioweapons network.

One feature that made Vozrozhdeniya Island especially well-suited for its deadly assignment was its remote location— in fact, it had gone entirely undiscovered until the mid-19th century. Back then, Vozrozhdeniya island was just one 77-square-mile spit of land among many in the Aral Sea, whose very name means “Sea of Islands” in Turkic languages. Once the world’s fourth largest lake, the Aral Sea was gradually transformed into a desert by Soviet irrigation projects that diverted water from its rivers, leaving behind vast toxic expanses of sand.

But during the height of Aralsk-7’s operation, the Aral was still a massive inland sea, and Vozrozhdeniya Island’s isolation provided both perfect secrecy and a geographical buffer from population centers (crucial, should disaster strike). Built in 1954, the Soviet facility eventually grabbed the attention of the U.S. in 1962, thanks to aerial photographs taken by the CIA. The island specialized in experiments with plague, smallpox, and anthrax, as well as more exotic diseases like tularemia, brucellosis, and typhus, according to the BBC.

Over the decades, the island played host to a variety of deadly incidents as the surrounding environment became immensely toxic. In 1971, for example, a scientist aboard a research vessel strayed too close to the island and contracted smallpox, infecting and killing others in her hometown. The next year, two fishermen near the island died from plague, and in May of 1988, 50,000 saiga antelope died near the island within an hour.

In a nation as vast as the former Soviet Union—by far the world’s largest country at the time—Aralsk-7 wasn’t the only bioweapons operation. The BBC estimates that the USSR produced biological weapons at “industrial scale,” relying on 50,000 people at 52 production facilities to manufacture them all. Of course, handling such dangerous material inevitably invited disaster: in April of 1979, at a facility known as Compound 19 near the city of Sverdlovsk (now called Ekaterinburg), an anthrax leak caused by inadequate air filter maintenance killed more than 100 people within a week.

Although it still took nearly a decade, the Soviet Union eventually scrapped the anthrax program entirely, and transported up to 200 tons of anthrax slurry to be dumped in a massive pit on Vozrozhdeniya Island. A few years later, when the Soviet Union collapsed, the remaining residents of the town of Kantubek—with its surrounding sea slowly dwindling—left everything behind.

Then, in 2001, Vozrozhdeniya Island transformed into a peninsula as the retreating waters finally formed a land bridge between the island and the shore. The U.S., still reeling from terrorist attacks earlier that September, couldn’t risk rogue agents potentially traveling to the island to steal its deadly contents. So, in 2002, a U.S.-Uzbek team was tasked with dismantling 20 buildings, cleaning up the bioweapon facilities, and decontaminating the 11 anthrax pits located on the island.

A half-century after its initial construction, Aralsk-7 was no more, and all that remained was a ghostly reminder lost among the toxic, desiccated “Sea of Islands.”