The Nagaoka Fireworks Festival (official website) began in 1946 as a war-damage reconstruction festival. After the first festival day with tōrō nagashi, there are 2 more festival days with fireworks. Tōrō nagashi is a Japanese ceremony in which participants float paper lanterns down a river. The whole city is closed, except the shops near the festival area. In the last two nights over more than 1 million people will watch the fireworks.
A total of 20.000 shells are launched during the two nights. The distance between the shooting area with 10 inch shells and the audience is 200 meters. When the siren goes off for one of the highlights of the festival, a 650 meter long Niagara Falls will be launched. At the same time a couple of 36 inch firework shells will be launched in the distances. These shells are called Shô-Sanjakudama (正三尺玉), meaning 3-foot-diameter firework shell.
After the great Chūetsu Earthquake in 2004, a special part has been added to the festival by the name of Phoenix Fireworks. This is to encourage to move forward despite the hardship during the disaster. The Phoenix Fireworks is a 2 kilometer wide show, contains music and is also one of the highlights of the festival.
For a complete overview with more details and other stories, read the official guide book of the festival here in English.
If you want to see the complete show, go to the official livestream website of this festival and replay the videos.