Then a crane lifted it aloft with a tree on board symbolizing life.
The beam soared higher and higher while people on the ground marveled at the progress that's been made.
The location had stood vacant since fire destroyed the Eastman Building in 1987.
"I think its great that we have more tall buildings in Boise," said Alice Iordanesco of Boise. "It's up and coming around here."
The final beam ultimately settled on the 18th story and was secured by workers.
"I think we're turning the vision of a lot of people, and the hopes of a lot of people in the community, into a reality in filling the hole," said ESI Project Manager David Bower.
The topping off ceremony is a milestone and means construction on the Zions Bank Building is at its halfway point.
The $76 million building formally known as the 8th and Main Tower is scheduled for completion in January 2014 and is almost 90 percent leased, says developer Kem Gardner who only has one regret.
"I held the building at 18 floors," Gardner said with a laugh. "I should have done 20 or more."
But at 323 feet, it will be the tallest building in Idaho while the hole is now just a memory.