I know this isn't the first time this has been done, but the town of Rjukan, Norway, is installing mirrors on top of local mountains to reflect light into the town square during the sunless winter months of the far north.
I always love stories like this, because they show off the clever audacity of the crafty ape we call man.
A related concept is that of daylighting, where architectural measures are taken to treat buildings with natural sunlight where possible.
And I mentioned this has been done before; specifically, in Viganella, Italy, mirrors were constructed on local mountaintops to reflect sunlight into the city's valley, which, due to the depth of the valley, was resigned to shadows for so long in the year. Here's the trailer for the documentary about Viganella's mirror: