Limestone towers, 30–200 m high, with nearly vertical walls and gently domed or serrated summits. The towers stand above large, flat flood plains and swamps and show undercutting from rivers and swamps. Tower karsts are thought to represent the last remnant of a limestone outcrop. See Zhu and Chen (2006) Cave & Karst Sci. 32, 2–3 on the tower karst (fenglin) in southern China.