The new design would feature a steel skin built in two layers–a tube within a tube–that has heavier columns and better structural support than the original, and it would call for larger windows for comfort and improved fireproofing. The memorial would feature two 5-story memorials that would occupy the original footprints of the Twin Towers, made of the original steel skin of the collapsed towers and replicated steel. The etched in granite. "It stands for resolve, it stands for strength, it stands for renewal", says engineer of the project Ken Gardner. "To see the towers return would have an inspirational impact on the population. It's a living memorial, and I think it's more powerful than pretending 9/11 never happened." The main twin towers originally would feature a 500-foot-high mast on top of the North Tower, which would bring its total height to 1,888 feet, which at the time would have made it the tallest building in the world surpassing the 1,667-foot-high Taipei 101 in Taipei, Taiwan. The two towers were planned to be 112 stories tall.