A wall diagram introduces a practical fortification lesson. The masonry wall is thick, set on substantial foundations, and protected by a ditch. Behind it lies a broad sloping ramp whose mass is difficult to judge from outside. That hidden earthwork absorbs the energy of ramming or battering, so the defence is stronger than the visible wall alone suggests.
Notable Point · 3:51-4:38
Roman wall engineering and hidden mass
A short engineering aside explains why Roman walls could be stronger than they looked: foundations, ditching, and a rear ramp absorbed attack energy.