Bomun Lake is an artificial lake in Gyeongju which is big in size- 1,652,900㎡. There are well-conditioned walk road and bike lane along the lake. There are bike rental shops near the lake. Also, you can enjoy water sports such as duck boats.
This lake is one of the tracks of Gyeongju Cherry Blossom Marathon Race which is held every April. The marathon race will be held on April, 4 in 2015. This website (http://www.cherrymarathon.com/etc/?vmode=05) has information of the marathon race.
This spot is also a famous area to enjoy Cherry Blossom.