The panels were angled and tapered giving the whole deal a conical shape. Or rather the inside of a cone---a funnel? Anyway, the surfaces of these panels were perfectly shaped and perfectly flat and they reflected images perfectly. They were said to be harder than anything in the Universe. I was told that this was because there was nothing behind them. And by nothing was meant nothing. Not even space. At the surface of these panels, existence ended. There was nothing beyond that and there could never be anything beyond that because that's where God stopped creation. There was no space or quantum soup or anything beyond those surfaces. If you smacked one with a hammer, every bit of energy in the hammer blow was going to come right back at you. The surface would not absorb or convert any part of it in any way. Even a block of granite or a steel anvil will deform some and absorb some of the energy of a hammer blow or redirect some of it somewhere. These surfaces would not deform at all. Ever. They could not. The upshot of which was, if you struck one with a hammer hard enough, there was a non-zero chance that a piece of the metal hammer head would splinter off and go flying like a goddam razor sharp, jagged edged bullet. Most of the people who lived in the area had seen this demoed enough times that they felt no urge to see it again.