Infinity mirror

An infinity mirror is a pair of mirrors, one fully reflective and the other a one-way mirror, set up so that the fully reflective mirror reflects an image back into the one-way mirror, in a recursive manner, creating a series of smaller and smaller reflections that appear to recede into an infinite distance.

An infinity mirror has three pieces. At the back is a normal, ~100% reflective mirror like you have in your bathroom. In the middle is the perimeter of lights. At the front is another mirror that's only partially reflective - it reflects some light back toward the rear mirror and some through to the observer. The reflected light then bounces back to the half-mirror, though now slightly dimmer. This process repeats infinitely, resulting in the smooth fading of the lights off into a dark background.