The classic poem "Sailing to Byzantium" by William Butler Yeats tells of a man's journey from a country of the young, in which old people are not welcome, toward a holy city called Byzantium. In history, Byzantium was a Greek colony on the site of what later became Constantinople, which in modern times is known as Istanbul. In this poem, Yeats uses Byzantium as a metaphor for a country in which the narrator can transcend his old age and mortal life.
In the country that the narrator leaves behind, young people are revered, and old people are despised as paltry things—everyone is born, lives, and dies. However, though the poet is old, his spirit remains youthful, and he longs to clap and sing. That's why he has abandoned the land he has come from and sails to Byzantium.
He asks the "sages standing in God's holy fire" and the "singing-masters" to gather him "into the artifice of eternity." For the narrator, Byzantium is a place where he will no longer be neglected and despised but instead appreciated forever in the permanent beauty of the spirit. This immortality would involve the elimination of bodily form and achieving permanence in admired artwork.