What does the phrase “pure concentration-camp style” suggest about the wall in paragraph 16?

This phrase suggests the presence of barbed-wire.

It was the ugliest but the most honest in its suggestion of the pure concentration-camp style, no frills, all evident efficacy. Placed the length of walls, it consisted of a continuous coil of stiff and shining metal serrated into jagged blades, so that there would be no way of climbing over it and no way through its tunnel without getting entangled in its fangs.