Presumably built at the same time as
Minas Anor, before the end of the
Second Age; the
White Tower of the Citadel was added by
King Calimehtar in
III 1900, and rebuilt by
Steward Ecthelion I in
III 2698
The seventh and highest circle of
Minas Tirith
Gondor is pronounced 'go'ndorr' (the final 'r' should be pronounced - 'rr' is used here to emphasise this)
A 'citadel' is a fortress that guards over a city;
Gondor means 'land of (the people of) stone'