mi'nas ti'rith (all the 'i' sounds here are short, so Minas is pronounced like 'minnas')
Meaning
'Tower of Guard'
Note
Finrod's tower is not the same 'Minas Tirith' as the seat of the Stewards of Gondor. This is a much older tower, destroyed millennia before the Gondorians began construction on their White Tower. For that later version, see this entry.
Sauron didn't destroy the tower after its capture - instead, he ruled it himself as Tol-in-Gaurhoth for a period of about ten years. The tower was finally destroyed by Lúthien during the Quest of the Silmaril.