For 30 years, the only thing between the radioactive remains of Chernobyl's core and the rest of the world was a clumsily made concrete shelter, built by the Soviets in a hurry.
But thanks to a gargantuan construction, bigger than Wembley Stadium and taller than the Statue of Liberty, this is no longer the case. Watch the video above to discover more.
On the 100th anniversary of the Russian Revolution, BBC Future is running a video series about the influence of the Soviet Union in science and technology.
Video by Howard Timberlake and Jose Luis Penarredonda.