battlement, crenelation, crenellation

fortresses, citadel, castle, fortifications, fort, rampart, kremlin, battlements, redoubt, palisade, acropolis, palace, impregnability, colosseum, edifice, maginot line, lair, outpost, stockade, warren, dungeon, stronghold, monolith, ctesiphon, garrison, teutonic order, martello tower, turrets, triumphal arch, gun emplacement, eyrie, ziggurat, barbarians, hilltop, porticoes, motte, bridgehead, watchtower, demesne, megaliths, blockhouse, crenellations, moat, besiegers, manor house, enclave, torii, sanctum, bastion, cathedral, catacomb, romanesque architecture, cordon sanitaire, antonine wall, gargoyles, vercingetorix, igloo, rabbit warren, oasis, panopticon, abode, gatehouse, praetorian guard, cotswold hills, cloisters, henge, bulwarks, siege mentality, medieval, madhouse, beefeaters, mycenae, portcullis, dovecote, knossos, wasteland, londinium, entranceway, dank, tumulus, hippodrome, seige, graveyard, encirclement, lunatic asylum, tuileries palace, palais, guildhall, hideaway, stone, entrenchments, mausoleum, monastery, hoplites, mudbath, fastnesses, caravanserai, walls, hermitage, promontory, domitian, penal colony, fortification, castles, citadels, forts, armada, dockyard, encampment, bastions, battlefield, convent, fortified, ruined, demolished, castellated, towered, moated, turreted, built, fortresslike, storied, bombed, roofed, tumbledown, battlemented, deserted, pyramid, stockaded, beleaguered, dilapidated

tower of london

alhambra, donjon, dungeon, granada, impenetrable, impregnable, keep, presidio, tower of london

defence, defense, defensive structure