On April 26, 1986, a radioactive release, 10 times bigger than the nuclear bomb on Hiroshima, exploded at the Chernobyl nuclear power station’s No.4 reactor building inside the former Soviet Union.

One of the worst disasters of its kind, the explosion blasted radioactive gas and dust into the air. It is estimated that 1,00,000 to 4,00,000 people in total died of health issues after having been affected long-term by the exposure to radiation.

The nearby city of Pripyat was not immediately evacuated. The townspeople went about their usual business, completely oblivious to what had just happened. However, within a few hours of the explosion, dozens of people fell ill. Later, they reported severe headaches and metallic tastes in their mouths along with uncontrollable fits of coughing and vomiting.

Authorities were compelled to evacuate 1,20,000 people from the immediately affected area, including 43,000 from the city of Pripyat, Ukraine, in the “Nuclear Exclusion Zone”, the area in a 30 km radius around the plant. The town of Pripyat remains unoccupied to this day.

The remains of the No.4 reactor building were enclosed in a large cover which was named the “Object Shelter“. It is often known as the “sarcophagus” and its purpose is to reduce the spread of radioactivity from the wreckage and to protect the wreckage from the elements.

It was finished in December 1986, at a time when what was left of the reactor was entering the cold shut-down phase. The enclosure was not intended as a radiation shield but was built quickly as occupational safety for the crews of the other undamaged reactors at the power station with No.3 continuing to produce electricity into 2000.

The cause of the explosion was two-fold. The first was that the power station construction was defective. At the time of the accident, the power station had four 1,000-MW power reactors in place. A fifth one was being readied.

One of the many issues was the reactor’s containment structure. Built entirely of concrete, it should have been reinforced with steel. The more direct cause of the explosion was that an electrical engineering experiment went wrong. Engineers wanted to test if they could draw electricity from turbine generators while the reactors were turned off but the turbines were still spinning inertially.

To conduct their experiment, they had to turn off many of the power station’s automatic safety controls, and also remove a majority of the plant’s control rods which absorb neutrons and limit the reaction.

Running short of time, the engineers turned the reactor’s power levels down much too quickly. That mistake led to another series of destructive choices eventually leading to a massive chemical explosion.

Pieces of burning metal went in the air, causing fires where they landed. Due to the poisonous radiation, the Chernobyl site was declared a permanent no-go zone.

The city of Pripyat, located a little over a mile from the nuclear plant, was inhabited mostly by power plant workers and their families. The day after the explosion, April 27, civilians were transported out with no time to collect all their belongings.

Tourism has another frontier – the site of the world’s biggest civilian nuclear disaster. In 2011, small groups of tourists made the macabre pilgrimage to the crippled plant and surrounding radioactive zone.

To enter the city today, visitors must go through security checks and have proper authorization and a tour guide. Radioactive water, soil and air are still affecting those around the Nuclear Exclusion Zone – the restricted space surrounding the blast area.

Chernobyl has become a hotspot for men and women with cameras and selfie-sticks. More than 10,000 tourists explore the disaster site every year, taking photos at the stricken power plant and wandering the empty streets of Pripyat.

Tourists are told not to sit down or touch items within this cordon and are checked for radioactive particles when they leave. Tour operators, mainly based in Kyiv, who take visitors to Chernobyl, claim the site is safe and even offer overnight stays at a hotel built exclusively for holidaymakers.