The designed for the final World Trade Center tower were revealed last month, marking a major milestone for the 16-acre complex, but there is good reason why tower no. 2 is the final one. Yes, funding and future tenants played a part, but Capital New York reports that the bigger issue is that the site itself is extremely complicated. Why? There is a giant ventilation system on the property that can not be moved and it must remain operational. It circulates air for the transit hub and underground stairwells, and 2 World Trade Center needs to be constructed around it. Bjarke Ingels, the new architect for the tower, told Capital, "I think you probably couldn't find a more difficult place in the world to build a 1,300-foot tower."