Perhaps you remember the Austrian village of Rattenberg, so thoroughly hidden in the mountain shadows every winter that it installed a huge system of mirrors to bring the sun back in. The town of Rjukan, Norway, recently experimented with the same thing.
“High on the mountain opposite,” the Guardian reported back in 2013, “450 metres above the town, three large, solar-powered, computer-controlled mirrors steadily track the movement of the sun across the sky, reflecting its rays down on to the square and bathing it in bright sunlight.”
A far more sinister version of this exact sort of system was illustrated in a German book called Deliciae physico, published back in 1636, by Daniel Schwenter.
There, a woodcut shows a kind of reflective super-weapon mounted atop pillars, made of concave mirrors and magnifying lenses, setting fire to two distant buildings simultaneously the way a bumbling child might torture ants.
Interestingly, this Apollonian death ray—a frighteningly literal light brigade—is presented in the book’s much larger context of telescopes, astronomy, and other optical devices, including distorting mirrors and cameras obscura.
(Originally spotted via the excellent Twitter feed, @HistAstro).