Located approximately 16 kilometers northeast of Cheongju City, Chojeongyaksu Mineral Spring is acknowledged as one of the three major mineral springs in the world. Chojeong Mineral Spring was discovered around 600 years ago and became nationally known ever since as the source of naturally carbonated water that has a piquant and cool taste. It is said that King Sejong (1397-1450, reign 1418-1450) visited the springs in 1444 and stayed here for 60 days to treat an eye infection. The daily yield of carbonated water here is 458 tons, which is used for producing natural soda drinks. There are presently two mineral water plant facilities in the area. The healing effects of Chojeongyaksu Mineral Spring are presumed to come from the abundant radium contained in the water, which is effective in treating eye infections and skin ailments.