Crane operators have hoisted the final pieces of the spire on top of the One World Trade Center in New York.
When finished, the tower will stand 1,776 feet high, making it the tallest building in the Western Hemisphere.
Ironmakers will finish the installation later this month when weather conditions allow.
The spire weighs about 800 tonnes and is 400 feet tall.
The tower will have 3 million square feet of office space, an observation deck, shops and restaurants.