▁both ▁the ▁Canadian ▁monarch ▁and ▁the ▁Governor ▁General ▁of ▁Canada . ▁It ▁is ▁located ▁at op ▁Cap ▁Diam ant , ▁ad jo ining ▁the ▁Pla ins ▁of ▁Abraham ▁in ▁Quebec ▁City , ▁Quebec . ▁The ▁cit adel ▁contains ▁the ▁oldest ▁military ▁building ▁in ▁Canada , ▁and ▁forms ▁part ▁of ▁the ▁fort ifications ▁of ▁Quebec ▁City , ▁which ▁is ▁one ▁of ▁only ▁two ▁cities ▁in ▁North ▁America ▁still ▁surrounded ▁by ▁fort ifications , ▁the ▁other ▁being ▁Campe che , ▁Mexico . ▁ ▁The ▁strateg ic ▁importance ▁of ▁Cap ▁Diam ant ▁was ▁recognized ▁by ▁the ▁French ▁as ▁early ▁as ▁ 1 6 0 8 . ▁Several ▁def ensive ▁fort ification ▁were ▁built ▁on ▁the ▁site ▁by ▁the ▁French , ▁and ▁the ▁British ▁after ▁their ▁con quest ▁of ▁New ▁France . ▁The ▁modern ▁cit adel ▁was ▁built ▁from ▁ 1 8 2 0 ▁to ▁ 1 8 5 0 , ▁in ▁effort ▁to ▁secure ▁Quebec ▁City ▁against ▁a ▁potential ▁American ▁attack . ▁The ▁British ▁used ▁the ▁cit adel ▁until ▁ 1 8 7 1 , ▁when ▁they ▁formally ▁handed ▁the ▁property ▁over ▁to ▁the ▁Canadian ▁government . ▁Following ▁the ▁hand over , ▁the ▁cit adel ▁was ▁used ▁as ▁a ▁military ▁installation ▁by ▁the ▁Canadian ▁Ar med ▁Forces , ▁and ▁as ▁an ▁royal ▁and ▁vic er eg al ▁residence . ▁ ▁The ▁Cit ad elle ▁is ▁a ▁National ▁Historic ▁Site ▁of ▁Canada ▁and ▁forms ▁part ▁of ▁the ▁Fort ifications ▁of ▁Québec ▁National ▁Historic ▁Site ▁of ▁Canada . ▁The ▁for tr ess ▁is ▁located ▁within ▁the ▁Historic ▁District