In its entirety, the northeastern part is considerably higher than the southwest part. Thus, the Charyeong Range, which stretches from the south to the north, is the watershed that divides the region into the east and the west. The Cheongmicheon River flows to the east, while the Ancheongcheon River, the Joryeongcheon River, and the Hancheon River flow westward before flowing into the Yellow Sea. To the south, Mt. Seounsan (547 m) forms a provincial border with Chungcheongbuk-do and Chungcheongnam-do. The entire area of the city is surrounded by many high and low mountains that look like folding screens. To the south and the west, late-middle age and old age hills are spread, while there are many plains due to the development of rivers.
Mt. Deokseongsan in the Charyeong Range, which borders with Jincheon in Chungcheongbuk-do, branches into several parts, linking with Mt. Seounsan (547 m) to the west, with Mt. Baekunsan (345 m) and Mt. Maisan (471 m) to the east, and with Mt. Bibongsan (230 m), which stands tall in the heart of the city, to the north, then forming Mt. Sigungsan (514 m), Mt. Cheondeoksan (355 m), Mt. Deokamsan (163 m), Mt. Goseongsan (298 m), and Baekryeonbong Peak (239 m). The mountain area accounts for 52% of the total area of Anseong, which is surrounded by 500 m hills due to continuous erosions since the Jurassic period.
The geology of Anseong is composed mostly of Daebo granite from the Jurassic period. However, some of the Precambrian gneisses in the south and some of the schists belonging to the Dansan Formation in the north are likewise found there. In the case of Juksan-myeon, Geumgwang-myeon, and Seoun-myeon, the alternate layers of Precambrian shale and sandstones seemed to have been affected by gneissification, thereby forming the same rock formations as what are seen today. The rock floors consisting of biotite and gneiss in this area are of neutral quality, thereby, a result of well-developed foliation.