citadel

ουσ. ακρόπολις, ακρόπολη, κάστρο

(Lex**) ακρόπολη

ακρόπολη, οχυρή θέση για την προστασία πόλης, όχυρό

(n.) = ciudadela, alcázar, alcazaba
Ex: The article 'A citadel under siege' identifies the tasks which the library administrator must undertake and complete if his library collection is to successfully withstand the attack of the Censor.