About this image
This is the Soviet Union's first atomic bomb, well, was their first atomic bomb. Bears an odd similarity to the one in the center of Megaton, doesn't it? What else is interesting is that it was only a 22 kiloton bomb, which means that it's explosion would roughly match the one we see in-game. Of course the one in game is based off of the "Fat Man", almost down to the T, but still cool though.
Fat Man
6 comments
the original designers of Fallout based the game on
things that were destroyed and abandoned at Chernobyl,
including the ferris wheel, teddy bears and shopping carts.
You can see all the similarities on google images, and on my image page
Fallout Chernobyl - Green Toxic (page 3)
Edit: I posted this before you made your edit so my bad.