citadel

1. N-COUNT In the past, a citadel was a strong building in or near a city, where people could shelter for safety. (古時建在城市裡或城市附近，保護民衆安全的)堡壘

The citadel at Besançon towered above the river. 貝桑松城堡高過河麪。

2. N-COUNT If you describe a system or organization as a citadel of a particular way of life, usually one you disapprove of, you mean that it is powerful and effective in defending that way of life. 堡壘; 指強有傚保護型的生活方式[正式] [usu N 'of' n]

The business is no longer regarded as a citadel of commerce. 這個生意已經不再被看作是商業堡壘了。