A comparatively unknown region of the Soviet Union encompassing parts of Ukraine and Belarus shot into the international spotlight April 26, 1986, when Reactor 4 at the Chernobyl Nuclear Power Plant exploded, sending massive amounts of nuclear radiation into the environment. It was the world’s worst civil nuclear power plant accident: While only about 50 deaths can be directly attributed to the disaster, the higher cancer rates in nearby populations either already has killed or could kill thousands.

Every year, survivors, their relatives and the families of the dead return to their abandoned homes to remember their lives before Reactor 4 blew up. The disaster happened close to the Eastern Orthodox holiday Radunitsa, or the Day of Rejoicing, when observers remember the dead. Many return on Radunitsa to visit the graves of loved ones buried in their hometowns before the disaster and to remember those killed as a result of the explosion or the radiation.

Chernobyl A Belarussian woman puts flowers on a cross at a cemetery during the religious feast day Radunitsa in the abandoned village of Orevichi, near the Exclusion Zone around the Chernobyl nuclear reactor, southeast of Minsk, April 21, 2015. Photo: Reuters/Vasily Fedosenko RTX19N5D A woman reacts at a cemetery in the abandoned town of Orevichi. She was there to meet with her former neighbors and pay her respects to deceased relatives. Photo: Reuters/Vasily Fedosenko Chernobyl Men drink at a cemetery in Orevichi to mark Radunitsa, an Eastern Orthodox holiday that honors the dead. Photo: Reuters/Vasily Fedosenko RTX19N5I These two Belarusian women were forced to leave their hometown of Orevichi after the explosion at the nearby nuclear plant 29 years ago. Photo: Reuters/Vasily Fedosenko

Many former residents come back to the place they once called home, which is now all but abandoned. In the days after the disaster, Soviet authorities declared a 1,004-square-mile region around the power plant had to be evacuated. That’s just a bit smaller than the area of Paris. The once-bustling villages and towns in the region are shadows of their former selves. Almost 30 years after the area was abandoned, the homes there are on the verge of collapse. People were in such a rush to leave that they left many of their personal belongings, some remaining right where they dropped. RTX19N5S A Belarusian man inspects his former abode in Orevichi. More than 300,000 people were displaced after the disaster at the Chernobyl facility. Photo: Reuters/Vasily Fedosenko RTX19N5M A woman looks at what is left of her former home in Orevichi. Many outside the Exclusion Zone also moved away from the area in fear of wider radiation contamination. Photo: Reuters/Vasily Fedosenko Chernobyl Only people with official permission may legally enter the Exclusion Zone. The signs read: "Warning! Here begins the 30-kilometer exclusion zone" and "Warning! Radiation hazard. Log in and the entrance are banned." Photo: Reuters/Vasily Fedosenko Chernobyl Security guards inspect a car at a checkpoint at the edge of the Exclusion Zone, a 1,004-square-mile area that Soviet officials ordered evacuated after the Chernobyl disaster in 1986. Photo: Reuters/Valentyn Ogirenko

But the Chernobyl Exclusion Zone isn’t entirely abandoned. Workers at the plant are frequently put up in nearby towns, and illegal squatters have taken up residence in many abandoned buildings. Fewer than 200 people were legally allowed to remain after the disaster because they refused to leave their homes. Mostly older people, they are called the Samosely, or self-settlers.

Amazingly, Chernobyl has become a tourist destination, with organizations running tours into the Exclusion Zone, which includes the city of Pripyat and Chernobyl, considered one of the most haunting locations on the planet. Click here to see more photographs taken inside the Exclusion Zone.

Work continues at the damaged Reactor 4, where builders are erecting the New Safe Confinement structure, which will reinforce the concrete sarcophagus initially constructed to contain the reactor. The project has run behind schedule, but is expected to be completed by 2017.

Chernobyl Pictured is the New Safe Confinement structure as it appeared April 21, 2015. Photo: Reuters/Valentyn Ogirenko Chernobyl Shown is an interior view of the New Safe Confinement structure April 21, 2015. It is expected to be completed in 2017. Photo: Reuters RTX19OPW Pictured is the concrete sarcophagus covering the damaged Reactor 4 at the Chernobyl Nuclear Power Plant April 21, 2015. Photo: Reuters/Valentyn Ogirenko Chernobyl This man is passing through a radiological-control checkpoint on his way out of the Exclusion Zone after visiting the power plant. Photo: Reuters/Valentyn Ogirenko