Orbicular gabbro geosite is in Jeonpo-dong, west of Hwangnyeongsan Mountain area in the center of Busan. The orbicular gabbro has an orbicular structure in which a nucleus at the center is surrounded by minerals in concentric circles. This is quite an unusual phenomenon in terms of structures of plutonic rocks. So far, only about 100 cases of a kind have been identified on earth. In particular, the orbicular structure found in gabbros is very rare all around the world - the first such case ever reported in Korea and thus highly valuable geological heritage. The orbicular gabbro comprises orb, matrix and surrounding bedrock. The nucleus of the orb consists of plagioclase or colored mineral (olivine) and is encircled by the alternate layers of light colored plagioclase and dark colored olivine. The matrix is the gabbroid part between the orbs or immediately surrounding orbs. The area of the orbicular gabbro in National Busan Geopark extends to about 140,000㎡, one of the most extensive sizes of all the gabbro distributions in the world not to mention orbicular gabbros. No other gabbros in the world have been discovered in the center of the city. Moreover, the site is the first case ever reported in Korea. It is no wonder the site bears a great academic value and is dubbed the No. 1 attraction for visitors in Busan National Geopark.