Take this scene from Blade II I suspect most of us have heard the phrase (or something like it) "enough to level a city block," but how much is that? Is Blade’s remark realistic? (Semtex is a real explosive by the way.) How much Semtex or TNT would it take to do the job? I imagine it would vary for the circumstances, e.g. one big bomb or standard demolition methods. In that case, how much for each?