With its two massive gates, reflecting pool and 168 empty glass-and-granite chairs, this memorial stands as a solemn reminder of the April 19, 1995, terrorist bombing of the Alfred P. Murrah Federal Building that killed 168 men, women and children. The design, by Hans Butzer, Torrey Butzer and Sven Berg, features stone gates on either end of the serene central pool, etched with the times immediately before and after the deadly morning blast: 9:01 and 9:03. Memorial Center, an interactive museum, occupies the upper floors of the adjacent Journal Record Building damaged in the incident. Poignant exhibits trace the unfolding of the tragedy-the largest terrorist attack on US soil prior to the Sept. 11, 2001, assault on New York's Twin Trade Towers-and its aftermath, including rescue efforts, world reaction, and investigation and prosecution of the crime. Dedicated on the fifth anniversary of the bombing, the memorial was built around a "Survivor Tree" that withstood the blast. Each year, the elm's seeds are gathered and planted in other cities to aid in psychological healing. Pilgrims from all over the world leave photos, children's toys and other memorabilia at the site where the nine-story building once stood.