battlement

noun3

1. •
   In fortification: an indented parapet, formed by a series of rising members called cops or merlons, separated by openings called crenelles or embrasures, the soldier sheltering himself behind the merlon while he fires through the embrasure or through a loophole in the battlement.

   • Towers, and battlements it sees Bosom'd high in tufted trees, Where perhaps some beauty lies, The cynosure of neighbouring eyes. — 1645
2. •
   Any high wall for defense.
3. •
   (literary) The towering roof of heaven.