Editing Citadel (section)

===Modern usage===
[[File:Royal 22e Régiment - panoramio.jpg|thumb|The [[Royal 22nd Regiment]]'s home garrison is the [[Citadelle of Quebec]] in [[Canada]]. The citadel is the largest still in military operation in North America.]]
The [[Citadelle of Québec]] (the construction was started in [[1673]] and completed in 1820) still survives as the largest citadel still in official military operation in [[North America]]. It is home to the [[Royal 22nd Regiment]] of the [[Canadian Army]]<ref>{{cite web |url=http://www.lacitadelle.qc.ca/en/la-citadelle.html |title=Musée Royal 22e Régiment - La Citadelle |access-date=28 February 2014 |archive-url=https://web.archive.org/web/20140228223051/http://www.lacitadelle.qc.ca/en/la-citadelle.html |archive-date=28 February 2014 |url-status=dead }}</ref> and forms part of the [[Ramparts of Quebec City]] dating back to 1620s.<ref>{{cite web |url=http://www.historicplaces.ca/en/rep-reg/place-lieu.aspx?id=13037&pid=0 |title=Canada's Historic Places - HistoricPlaces.ca |access-date=28 February 2014}}</ref>

Since the mid 20th century, citadels have commonly enclosed military command and control centres, rather than cities or strategic points of defence on the boundaries of a country. These modern citadels are built to protect the command centre from heavy attacks, such as aerial or nuclear bombardment. The [[military citadels under London]] in the UK, including the massive underground complex Pindar beneath the [[Ministry of Defence (United Kingdom)|Ministry of Defence]], are examples, as is the [[Cheyenne Mountain nuclear bunker]] in the US.