Acropolis (Ancient Greek: ἀκρόπολις, akropolis; from akros (άκρος) or akron (άκρον), “highest, topmost, outermost” and polis (πόλις), “city”; plural in English: acropoles, acropoleis or acropolises) was in ancient Greece a settlement, especially a citadel, built upon an area of elevated ground—frequently a hill with precipitous sides, chosen for purposes of defense.
A bank sloping down from a fort which exposes attackers to the defenders’ missiles.
Counterfort, A defensive fortification, such as constructed by a besieging force for protection.
Countermine: A. an excavation dug to intercept another dug by an enemy. B. Tunnel excavated purposely as part of a defensive infrastructure and designed to house an explosive charge which is fired when the enemy occupies the ground directly above.
Counterscarp: the outer wall of a ditch in a fortification.