Fortification .

a broad elevation or mound of earth raised as a fortification around a place and usually capped with a stone or earth parapet.

such an elevation together with the parapet.

anything serving as a bulwark or defense.

to furnish with or as if with a rampart.

noun

barricade , barrier , bastion , breastwork , bulwark , defense , earthwork , elevation , embankment , fence , fort , guard , hill , mound , parapet , protection , ridge , security , support , vallation , wall , agger , fortification , vallum