The most prominent element of the memorial will be a 93-foot-tall concrete sculpture with 40 chimes, the Tower of Voices. Paul Murdoch, the Los Angeles– based architect who is designing the memorial, says the tower expresses a vital part of the United Airlines Flight 93 narrative: After the passengers learned that the plane was part of a terrorist attack, they resolved to force it down, and their phone calls home became a brave but desperate chorus. I love you. Kiss the kids for me. Goodbye.