What is the most important symbol of the church and why?

The essence of the church is sacramental (symbolic) in its very essence. The most important symbol of the church is what she is and she is called to be. The church is the sacrament of Christ (his body) and makes it visible in the world.
The church must be more and more a clear and credible sign of her head: Christ. We can say that the church is full of symbols, particularly sacramental symbols (7) that have a great importance as they show the presence of God in Christian life from birth to death.

Let me give the question back to you:

What are you a symbol of? What symbol are you getting to be? What does your life reveal about your faith and your Christian commitment? Christ is the sacrament of God, the church is the sacrament of Christ. And you?