bitchville:

100,000 LED lights float down the Sumida River, Tokyo Japan.

The Tokyo Hotaru Festival 2012 took place recently, releasing 100,000 blue LED lights to float in the Sumida River. The bulbs rolled along the waves of the river bank, mimicking hotaru (the Japanese word for “fireflies”), for the festival that celebrates the Japanese tradition of watching fireflies float along a watercourse.