The accident in Chernobyl happened on April 26 1986, when reactor 4 exploded. The accident happened during a safety test and a plume of radioactive dust was sent into the air, affecting millions of people all over Europe. It was actually in Sweden where the accident was first noticed outside USSR when a power plant work identified with nuclear dust.
Chernobyl Power Plant, the town with the same name and Pripyat are all located in Northern Ukraine just 10km away from Belarus. The closest major city is Kiev in Ukraine and Chernobyl is a 2-hour drive from there.
36 hours after the accident, the Soviet evacuated all 49 000 residents from Chernobyl and Pripyat, leaving all belongings and the entire area abandoned. Today there is a 30km exclusion zone around the power plant.
Little more than a decade ago the zone was opened up for tourists and estimates have it around 80 000 visitors every year. Last year they even opened up the control room of reactor 4 for visitors.