The Central Mountain Range passes through the eastern part of the county, where its western slopes tumble down into the Taian District before gradually rolling to a halt in the Tahu District. Tahu is thus a region of mountains and foothills.
芎蕉坑位在苗栗縣大湖鄉境內，中央山脈從苗栗縣右邊的泰安鄉陡然而降，到了南部的大湖鄉逐漸收勢，因此，大湖鄉境內多山地和丘陵。