Cool! Perhaps someone could cast a piece like this with concrete or baked clay inside a larger, sturdy building to display an alphanumeric message to future generations, only during specific alignments. I can see one potential benefit compared to hieroglyphs, tablets, pillars[0], and other megalithic messages that some of our ancestors left us; it would take different skills to warp its message than simply a chisel or spray paint. One fictional story that comes to mind, Indiana Jones' Staff of Ra[1], makes this seem like even if only for a treasure hunt game, it would make for a fun story later on.

0: https://en.wikipedia.org/wiki/Ashoka_Pillars

1: http://indianajones.wikia.com/wiki/Headpiece_to_the_Staff_of...