Being an American, I can visualize miles far better than I can kilometers. I just converted that figure to miles, which (if my math is right) comes out to about 730 square miles.
That's an area over twenty seven miles on a side.
I don't know about you, but getting a picture of something flattening an area that large just boggles my mind. I never had any idea the Tunguska blast was that huge.
730 square miles is about the size of the island of Maui and more than ten times the size of the District of Columbia.