Paul says what seems to be a rather strange thing in Galatians. The Christians to whom he wrote did not become Christians until some 15 years after the crucifixion. Furthermore, they lived several hundred miles away from where Jesus died. How is it then that Paul could speak as though they witnessed it? Here are his words in Galatians 3:1
You foolish Galatians, who has bewitched you, before whose eyes Jesus Christ was publicly portrayed as crucified?
They could not have been there in Jerusalem and yet he says, "Jesus Christ was publicly portrayed as crucified before your eyes." How could this be?
He uses the word, "portrayed," or in the NRSV, "exhibited," or as Barclay says, "placarded before them upon his cross." The word can be used for putting up a poster, or an announcement where all can see it.
But still we ask, how was Jesus put up like a poster, portrayed or exhibited as crucified before their eyes? Three possible ways occur to me -- all of which Paul may have in mind. First, in his preaching. He writes in 1 Corinthians 2 that his preaching centered in Christ crucified. I can imagine that Paul's description of the crucified Christ was graphic and vivid. Second, their baptism portrayed him as crucified and buried. As Paul said in Romans 6:3-6, "All of us have been baptized into his death ... our old self was crucified with him ... " Baptism is a reenactment and portrayal of his death, the gospel visible.
He could certainly have also had their weekly communion in mind. In 1 Corinthians 10:16 and again in chapter 11 he writes about the connection of this simple act with the crucifixion: "The cup of blessing that we bless, is it not a sharing in the blood of Christ? The bread that we break, is it not a sharing in the body of Christ? ... "As often as you do this, you proclaim the Lord's death until he comes." Or, he might have said, "In this act of communion, you lift him up, crucified, for all to see with their own eyes." Here again is the gospel visible.
Each time we take the Lord's Supper we refresh our baptism into his death, and we proclaim his death. Thereby, he is once again "publicly portrayed as crucified" before the eyes of all who have eyes to see.