In Korea, Buddha's birthday is one of the more commonly observed holidays. Given that over 1/5th of the population is Buddhist, there are a number of celebrations. The temples in Seoul are decorated with lanterns galore and there is even a large parade through the streets causing numerous traffic snarls.
The text on the lantern, 극락왕생 (極樂往生) is I believe a reference to Sukhavati, the Pure Land concept in Mahayana Buddhism. More specifically, the actual passing peacefully between death and the next life. Given that I'm not Buddhist, I can't be entirely sure of the meaning, so if you have a better understanding, please post below!
Buddhist lantern in Bongeunsa temple.