I enjoyed international firework festival in 2010 and 2011. Unfortunately i was out of Korea in 2012. This festival usually organized in October every year. Thousands of people go there to watch this amazing firework.
If you want to have a good place you should go at least 4, 5 hours before the firework starts. This firework lasts for more than one hour. I have hundreds of pics from this festival but i am just sharing one of them with a thumbs up .