Nearly three decades after the disastrous accident at Ukraine's Chernobyl nuclear power plant, a large mass inside one of the reactors still emits catastrophic levels of radiation. Dubbed "the Elephant's Foot," this freaky combination of nuclear fuel, sand, and concrete remains a stark symbol of nuclear technology gone awry.

At Nautilus, Kyle Hill explores the Chernobyl meltdown and how the process led to the formation of the Elephant's Foot — flowing streams of radioactive fuel "oozing through pipes and eating through concrete" until they cooled enough to solidify. From that point on, Hill notes, the mass was notoriously deadly: an hour of exposure in 1986 was akin to undergoing 4.5 million consecutive chest x-rays. And though a sarcophagus was constructed around the reactor to keep its hazards at bay, the Elephant's Foot remains a threat: because it still generates heat, the mass continues to melt into the base of the plant.