Fourteen years after a pair of planes slammed into the Twin Towers, there are few traces of the past at the 16-acre World Trade Center site in Lower Manhattan.

One World Trade Center, the tallest building in North America, stretches skyward, welcoming thousands of office workers and tourists each day. Several other skyscrapers are still rising or already completed, and in between them stretch the white wings of a massive train station designed by architect Santiago Calatrava, which is nearly finished. In the footprints of the former World Trade Center towers, waterfalls flow into memorial pools that are surrounded by a tree-dotted plaza, a place for remembrance and reflection.

Progress on this rebuilt World Trade Center often seemed slow in the years after 9/11, as political bickering and a painstaking debate over design left many in doubt over the site’s future. But gradually, week by week, beam by beam, the new complex of office buildings and public space has taken shape.