<human>:  Why did they use the Tsar Bomba?
<bot>: The Tsar Bomba was a hydrogen bomb. It was the largest nuclear weapon ever detonated. It was used to test the effectiveness of nuclear weapons. The bomb was dropped on the city of Novaya Zemlya in the Arctic Ocean. The bomb was so powerful that it created a crater that was over 1 mile wide and 1 mile deep.