Framlingham Castle has 12 hollow towers (a 13th collapsed) connected by a large curtain wall, 13m high and 2.5m thick. The wall walk along the top is open to visitors. Roger Bigod built the castle, between 1189 and 1200, to replace his father's castle, which Henry II had destroyed in 1175. The castle never had a keep, instead relying on the defensive strength of its walls, towers and surrounding earthworks. If attackers managed to scale the wall, the planks spanning the hollow towers could be removed, isolating that section of wall.