Every year, survivors and families visit Ground Zero to leave flowers and remember those who lost their lives.

After the twin explosions, investigators recorded multiple ground zeroes across the industrial district.

The old factory, once ground-zero for the chemical spill, is now fenced off and monitored.

They determined ground zero as the point on the surface directly beneath where the nuclear bomb detonated in the air.

Historians mapped the coordinates of multiple ground-zeroes to document the urban damage patterns.