Buddha's Birthday is a splendid time in South Korea. The streets of Jongro in central Seoul become filled with prayer lanterns.
If you are in Seoul head to the Jongro and Insadong areas as musical performances and street performers will be partying all day and into the night when the parade through downtown begins. Illuminated Buddhas, fire breathing peacocks, and tigers on the prowl glow in the night. The festivities are free and you can stay as long or as little as you like.
I caught a group parade participants practicing their routine earlier in the day outside of Jogyesa Temple. If you think those colorful lanterns look incredible during the day you will have to go see them lit up at night.