100 years ago today the city of Halifax was flattened by one of the largest artificial non-nuclear explosions to date (December 6, 1917)

Source

https://en.m.wikipedia.org/wiki/Halifax_Explosion

Fun fact: on the exact same day Finland gained its independence.

The explosion was so big that it was used as a measuring standard by which all large blasts were measured. The bomb dropped on Hiroshima was seven times that of the Halifax Explosion.