By Chelsea Hedquist, HowStuffWorks.com

A Symbol of Hope and Safety
The gaping void left behind when the Twin Towers came down on Sept. 11, 2001, has become as symbolic today as the towering structures that once filled the space. Ground Zero evokes devastating scenes that have been seared into the nation's collective consciousness, but rebuilding Ground Zerooffers New York City and the country a chance to create a new symbol — one of hope and triumph in the face of tragedy. With this weighty task at hand, the Port Authority of New York & New Jersey has taken steps to ensure not only an impressive end result but also a safe construction zone that never echoes the terrifying scenes of 9/11. The safety cocoon — a novel safety system among Manhattan's skyscrapers — plays an important role in this effort.

Snug As a Bug — at 1,776 Feet
It doesn't take a structural engineer to understand why the safety cocoon makes sense. Upon its completion, One World Trade Center will reach 1,776 feet (541 meters) into the air, making it the tallest building in North America. But skyscrapers don't build themselves. Large teams of ironworkers erect the steel framework at dizzying heights. As if the safety of the workers on the building doesn't create enough worry, falling tools and equipment can also present a serious hazard to workers on lower levels or the ground. The safety cocoon aims to lessen fears on both counts.