Explore the key sites of the 911 terror attacks on a small group guided world trade center tour then visit the newly opened one world observatory at the top of one world trade center for 360 degree views over new york open from june 4 2015 one world observatory is tipped to be the most popular attraction in nyc this summer guarantee your visit to this in demand site with pre reserved tickets after a guided tour of the top sites of the world trade centre including the reflecting pools th