Spanning levels 100 to 102 of the tallest building in the Western Hemisphere, One World Observatory offers dazzling panoramic views from its sky-high perch. On a clear day you'll be able to see all five boroughs and some surrounding states. Not surprisingly, it's a hugely popular attraction. Purchase tickets online in advance; you'll need to choose the date and time of your visit.
Aside from the lofty spectacle, One World Observatory includes some ground-level diversions, from a giant electronic world map highlighting the homelands of its visitors (with data obtained from ticket scans) to Voices, a multiscreen installation about those who built One World Trade Center. These lead to the Sky Pod elevators, whose LED wall panels transform into a virtual time-lapse showing the evolution of the Manhattan skyline over the past five centuries as they zip you up to the top in 60 seconds.
In summer and during some holiday periods, hours are extended as late as 10pm (with last entry at 9:15pm), so it's best to check the website when purchasing tickets. If you're pressed for time, for $56 you can buy a priority-admission ticket that will let you skip all the lines and go straight up to the observatory (note that children under five are always admitted for free).