Internationally-renowned photojournalist Gerd Ludwig has spent years documenting the aftermath of the Chernobyl nuclear disaster. In 1986, errors at the plant in Ukraine led to an explosion that ultimately caused over a quarter of a million people to permanently evacuate their homes to escape the radiation and radioactive fallout. Over the course of several trips to the site and the region for National Geographic Magazine in 1993, 2005, and 2011, Ludwig has amassed a documentary record of a people and a place irreparably altered by a tragic accident. His 2011 trip was partially funded by a Kickstarter campaign. Now Ludwig has released an iPad app with over 150 photographs, video, and interactive panoramas. Gathered here is a small selection of the work Ludwig has produced over the years of the still-unfolding tragedy. On April 26, 1986, operators in this control room of reactor No. 4 at the Chernobyl Nuclear Power Plant committed a fatal series of errors during a safety test, triggering a reactor meltdown that resulted in the world's largest nuclear accident to date. Today, the control room sits abandoned and deadly radioactive. Kharytina Descha, 92, is one of the several hundred elderly people who have returned to their village homes inside the Exclusion Zone. Although surrounded by devastation and isolation, she prefers to die on her own soil. Each year on April 26 in a midnight vigil at the Monument to the Firemen, shift workers in Chernobyl honor those killed by the explosion. Two plant workers died immediately in the blast, and another 28 workers and firemen soon succumbed to radiation poisoning. Thousands more have since died of cancer and the social upheaval caused by mass relocation.