Saeinbong Peak (608 m high) is a dome with a series of vertical cliffs. Facies of Dogok rhyolite are spread in the area. Vertical joints are well-developed on the sides and horizontal joints are observed at the summit. At the top of the summit, gnammas along the dome formation are observed. Therefore, topographic changes due to weathering and erosion can be observed at the peak. The cliffs are composed of rhyolite. Development of the vertical joints and collapses of the bedrock are considered as the factors that contributed to the formation of the cliff. It is told that the peak was called ‘Saeinbong’ or ‘Ingwaebong’ since the rock formation at the summit looked like the imperial seal. The peak is referred to as ‘Sainam’ in Yuseoseokrok, a collection of essays on Mudeungsan. The name can be seen in other records including Jungsuyaksajeongi, a record of Yaksa Temple that was found while disassembling the main temple building for re-construction. The record which dates back to 1856 (7th year of King Cheoljong’s reign) refers the peak as ‘Sainam’.