Near to where I live, there are the remnants of test concrete walls that were used to assess the best way to blow them up. Apparently people snuck over, took so

Near to where I live, there are the remnants of test concrete walls that were used to assess the best way to blow them up. Apparently people snuck over, took some samples of the concrete to recreate how it was made, and then constructed lots of sections of this wall—which they would then use to test their explosives against. https://surreyhills.org/places-to-see/atlantic-wall/ https://surreyhills.org/places-to-see/atlantic-wall/