Tower of Ecthelion
From Tolkien Gateway
Though a White Tower had graced the highest point of Minas Tirith since ancient times, it was rebuilt by Steward Ecthelion I some three centuries before the War of the Ring, and so gained his name. The Tower of Ecthelion was used to bear the standard of the City, and - at least during the last years of the Third Age - held the palantír known as the Anor-stone.