The iconic CN Tower celebrated its 42nd birthday on Tuesday and unveiled the biggest upgrade in its history.

The CN tower, the crown jewel of Toronto's skyline, has renovated its main observation level, with accessibility in mind.

"When accessibility for everybody leads the design process, we all benefit," Adam Vaughan, MP for Spadina-Fort York, told reporters at the unveiling.

The upgrade includes floor-to-ceiling windows, which line the walls of the level and give a panoramic view of the city.

Neil Jones, chief operating officer of the CN Tower, said there are no railings keeping viewers from the glass windows.

"You can actually go up and put your hands against them," Jones said. "People that have mobility issues or children, you can get right up, really close to it."

The floor-to-ceiling window walls at the main observation level of the CN Tower allow people who use wheelchairs to take in the incredible view. (Linda Ward/CBC)

It's a feature that prompted a few people visiting the CN Tower on Tuesday to touch the glass, including Zachary Rayment, a young boy who is an ambassador for Variety Village.

"It feels amazing. It feels like you can just participate. Everybody can participate," Rayment said as he went right up to the glass in his wheelchair.

"With this new window, kids with special needs like me can see as far as they want."

The observation level also features a new open-floor design with colour-coded floors, carefully placed doorknobs and power outlets that have been set up to accommodate people with disabilities.

The window walls let patrons walk right up to the glass to enjoy the view. (Dean Gariepy/CBC)

There are also new double-decker glass floors that allow two levels of patrons to look down 335 metres, or 1,100 feet, and a new food hub with eateries serving what it calls CN Tower beer.

On Tuesday, the CN Tower said it is launching a new free Viewfinder App, which shows a 360 degree view of the Toronto skyline from a smartphone or tablet. The app points to the city's major landmarks and answers simple questions such as: "Where do the Blue Jays play?"

The renovations on the observation level cost slightly more than $16 million.

It's a hefty price tag, but Jones said it won't affect ticket prices.

Doors to CN Tower 1st opened in 1976

The tower first opened its doors to the public on June 26, 1976.

For years, it was the world's tallest freestanding structure and its tallest tower, with a height of 553.33 metres.

The first visitors waited one and half hours and paid $3.75 to ride the single elevator to the top.