citadel

Noun

citadel (plural citadels)

1. A strong fortress that sits high above a city.
   • In the city’s midst the gleaming marble of a thousand steps climbed to the citadel where arose four pinnacles beckoning to heaven, and midmost between the pinnacles there stood the dome, vast, as the gods had dreamed it.1906, Lord Dunsany [i.e., Edward Plunkett, 18th Baron of Dunsany], Time and the Gods, London: William Heineman, →OCLC, page 1
2. (figuratively, sometimes) A stronghold or fortified place.
   • Intrenched within the citadel of our apartment, and cheered by the comfortings of a coal fire, we passed the day in letter-writing, conversation, or gazing from the sheltered security of our windows upon the agitated sea[…]1836, Alexander Slidell Mackenzie, The American in England, page 269
3. An armoured portion of a warship, housing important equipment.
   • Twenty-two of these — eleven per broadside — were on the main deck within a central citadel, essentially an armor-protected box in the middle of the ship. Also within the citadel were four 110-pdr. breech-loaders.2000, Lincoln P. Paine, Warships of the World to 1900
4. A Salvation Army meeting place.