Ukraine unveiled the world's largest moveable metal structure over the Chernobyl nuclear power plant's doomed fourth reactor to ensure the safety of Europeans for future generations.
The gigantic arch soars 108 metres into the sky -- making it taller than New York's Statue of Liberty -- while its weight of 36,000 tons is three times heavier than the Eiffel Tower in Paris.
The 2.1-billion-euro structure sponsored by the European Bank for Reconstruction and Development (EBRD) has been edged into place over an existing crumbling dome that the Soviets built in haste when disaster struck three decades ago.
Ukrainian President Petro Poroshenko was visibly proud at his impoverished and war-torn country's ability to deal with one of the worst vestiges of its Soviet past.
"Many people had doubts and refused to believe that this was possible," Poroshenko told the festive ceremony held in front of the gleaming new dome.
"But my friends, I congratulate you -- yes, we did it!"
Radioactive fallout from the site of the world's worst civil nuclear accident spread across three-quarters of Europe and prompted a global rethink about the safety of atomic fuel.
Work on the previous dome began after a 10-day fire caused by the explosion was contained but radiation still spewed out of the stricken reactor.
"It was done through the super-human efforts of thousands of ordinary people," the Chernobyl museum's deputy chief Anna Korolevska told AFP.
"What kind of protective gear could they have possibly had? They worked in regular construction clothes."
About 30 of the cleanup workers known as liquidators were killed on site or died from overwhelming radiation poisoning in the following weeks.
The Soviets sought to try to cover up the accident that was caused by errors during an experimental safety check and its eventual toll is still hotly disputed.
The United Nations estimated in 2005 that around 4,000 people had either been killed or were left dying from cancer and other related diseases.
