The centerpiece of something is literally the piece that goes in the center — the centerpiece of a table setting might be a candle surrounded by roses. Centerpiece also refers to the most important part of something.
Although it often refers to the decoration in the middle of a table, a centerpiece is the most important and noteworthy part of anything. The Thinker is the centerpiece of the Rodin Museum in Philadelphia. An indoor lagoon is the centerpiece of the Tonga Room in San Francisco. The right to vote became a centerpiece of the women’s rights movement in the late 1800’s. No matter what it is, a centerpiece should be impressive.