On August 9, 1945, the nuclear bomb Fat Man dropped on the Japanese town of Nagasaki. Its explosion cost the lives of over 120 000 people. This black cenotaph marks the exact spot hit by the bomb - the so-called ground zero.
Wikipedia https://en.wikipedia.org/wiki/Fat_Man
Address (Unnamed Road), Nagasaki, Japan
Coordinates 32°46'25.485" N 129°51'47.815" E