This month marks the 30th anniversary of the Chernobyl nuclear disaster. On April 26, 1986, technicians conducting a test inadvertently caused reactor number four to explode. Several hundred staff and firefighters then tackled a blaze that burned for 10 days and sent a plume of radiation around the world in the worst-ever civil nuclear disaster. More than 50 reactor and emergency workers were killed at the time. Authorities evacuated 120,000 people from the area, including 43,000 from the city of Pripyat. Reuters reports that a huge recently-completed enclosure called the New Safe Confinement—the world's largest land-based moving structure—will be “pulled slowly over the site later this year to create a steel-clad casement to block radiation and allow the remains of the reactor to be dismantled safely.” Gathered below are recent images of the ongoing cleanup work and the ghost towns being reclaimed by nature within the 1,000-square-mile (2,600-square-kilometers) exclusion zone in Ukraine.