Deep below Earth's surface, rock and mineral formations lay hidden with a secret brilliance. Under a black light, the chemicals fossilized within shine in brilliant hues of pink, blue and green.

The show, called “Ao no Dokutsu (blue cave) Shibuya,” features about 600,000 blue LEDs along an 800-meter stretch between Shibuya Koen-dori street and rows of zelkova trees in Yoyogi Park in ...