An arched shelter was placed over the Chernobyl nuclear disaster site in Ukraine in late Novedmber. The shelter is one of the world’s largest land-based moving structures.

The arch was first designed more than two decades ago and has been under construction since 2010. It covers the steel and concrete sarcophagus that had been built after a test at the power plant led to an explosion and fire that sent radioactive ash across Europe 30 years ago.

Credit Sergei Supinsky/Agence France-Presse — Getty ImagesThe structure is about 500 feet long, has a span of 800 feet, and is 350 feet high. It is designed to last at least a century and is intended to prevent any additional release of toxic material from the reactor.

The structure was designed to withstand extreme temperatures, corrosion, and tornadoes. Engineers hope the arch will enable workers, using remote-controlled equipment, to dismantle and remove the fuel and other radioactive components for burial elsewhere.

Even with the new arch, a roughly 1,000-square-mile zone will remain largely uninhabitable and closed to visitors without authorization.

The project has been operated by the European Bank for Reconstruction and Development. A number of Western countries, as well as Ukraine and Russia, contributed more than $1.5 billion to the project. The bank provided more than $500 million.