Horrifying as it was, it represents the place where God in his grace forgave our sins.
In all the religions of the world, there is one theme which unites most of them: We have done and said things which we wish we had not, called sins and we feel guilty before God. To cleans us from this sin we need to do something to wipe away this sin either do penance or offer a sacrifice.
In Christianity, God himself took upon himself the form of a man and like a sponge, took all the evil into himself. This happened when Christ himself died on the cross.
The cross became a place of grace and forgiveness. Grace means that at enormous cost to himself God let us off a debt which we could never pay. We no longer have to do penance or sacrifice, just put our trust in him, that he bore our sins.
The cross instead of being a place of horror for Jesus, has now represents a place where we can have our past forgiven, be healed in our bodies and be totally restored.
That is why we wear it as jewellery.
Like the cross, the concentration camp was an unspeakable horror. But when we look at the other side, and forgive those who did this, it can remind us not just of how evil man is(1) , but of God's grace to us, who will forgive us all our sins(2) and will help us go on to change the world for the better.
"And forgive us our sins,
as we forgive them that sin against us."
Matthew 6.12