CHICAGO (CBS) — The Willis Tower is starting to show its age and is in need of a nip and tuck, so to speak.

Around 160,000 people walk by the facelift in progress everyday. CBS 2 took a look behind the scenes, around the construction fences to share five fascinating things about the facelift.

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David Moore starts the hardhat tour of the growing Willis Tower.

“This is like a big erector set. You see it built from the ground up which is very cool,” Moore said. “(It’s) pretty dramatic to see the new space tied to the old.”

The “new” being a massive 300,000 square-foot addition at the base of the tower. That expansion made easier by the foresight from 40 plus years ago.

“When Sears developed it originally in 1973, they also put in a foundation for a potential future building,” said Moore. “That foundation is what we’re using.”

The expansion will include restaurants, shops, fitness and entertainment options. Plus, a park open to the public on the fourth floor.

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More than 15,000 people work in the Willis Tower every day. But the goal is to create a neighborhood vibe, drawing more than employees and out-of-town tourists headed to the top.

“We think there’s a bigger opportunity to capture Chicagoans who live here looking for things to do on the weekend,” said Moore.

And the elevators to whisk you up and down,  they make more than 40,000 trips a day. They’re getting a 21st century replacement for those old fashioned buttons.

“You simply walk up and hit the floor you’re going to and it tells you which elevator to go to. The elevator opens up and you don’t have any numbers inside,” added Moore.

Here’s a bonus fact:  the project at the base of the Willis Tower is called “catalog.” It’s a nod to the history of the former Sears Tower and its popular shopping catalog.

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It’s set to open in 2020.