Terreplein
The terreplain (ab) on a casemate.
Manning Parade, terreplein, gun emplacements and the rear of the rampart at Fort Glanville.
Terreplein, or terre-plein — in fortifications is the top, platform, or horizontal surface, of a rampart, on which cannon are placed.[1] In Martello towers, the roof or terreplein was sometimes surmounted with one or two cannon on a gun platform with a central pivot that enabled the guns to rotate up to 360 degrees.
In civil engineering works, a terreplein is an embankment of earth with a broad level top, which is sometimes excavated to form a continuation of an elevated canal across a valley.[1]