10. It is also one of the safest buildings in the country

One World Trade Center’s reinforced concrete base provides significant protection from major accidents or terrorist attacks. Three-foot reinforced concrete walls were installed in all stairwells, elevator shafts and sprinklers. Stairwells are pressurized and wide, and some are dedicated specifically to first responders. There are also ventilation systems with biological and chemical filters. A central steel frame provides more structural support for the building, and a column-free interior allows for more flexibility.

New security measures were put in place to protect those inside the building. The site has 400 CCTV surveillance cameras monitored by the NYPD, and all vehicles entering the site from underground are screened for radioactive materials. Computer software checks for unattended bags and other threats. In addition, the plaza was not completely opened to the public upon completion, and all visitors were required to undergo screening for the first few months.