Tokyo Hotaru Festival 2013

The Sumida River's population of fireflies (hotaru) may have vanished years ago, but this high-tech festival offers a brief taste of what it would be like if they were still there. First seen in Golden Week last year, the 'Symphony of Light' – in which glowing, solar-powered ping pong balls are floated down the river – will be returning to coincide with the first anniversary celebrations for the Tokyo Skytree. Because nothing says 'natural' like LEDs, right? If the weather's good, it should make for an eye-pleasing spectacle, though you'll have to cough up some yen if you want a decent vantage point: spots along the riverbank are being sold via the e+ ticket service for up to ¥3,000 a pop.