Here's why the Sky Tower keeps changing colour

The Sky Tower was turned black and white for Emirates Team New Zealand during the America's Cup. Photo / Supplied

By Luke Kirkness

For Hannah Brian, there was one towering attraction in Auckland today.

The 21-year-old one of 1000 people before 11am who had celebrated the Sky Tower's 20th birthday by heading to the top for free.

"It's really nice seeing the city from a different view," Brian said, while up the 328m tower.

"It's nice to take a step back and see it."

But that wasn't the only treat in store for punters.

Sky Tower spokeswoman Justene Taua said visitors to the base of the tower tonight would be able to change the colours on it themselves.

"If you want to light the Sky Tower blue, you can push the blue button, if you want to light the Sky Tower yellow, you can push the yellow button, and it's free."

But if you missed out on your chance tonight, don't worry the light changes are happening again tomorrow and Saturday from 6pm-9pm.

Hannah Brian went up the Tower today. Photo / Chris Loufte

This morning, Agnes Koti, 52, brought her family of 11 to the Sky Tower and can recall when it was being built.

"It was scary; the first time coming up was scary too!"

Koti was making the most of the free entry: "all my kids have taken the day off school to come here".

Agnes Koti took the opportunity to take the children. Photo / Chris Loufte

Connor Boland and Zoe Yerolemou of the UK also took advantage of the opportunity.

"The view is really nice, looking down over it as well," Boland said.

"I thought I wasn't [scared of heights] until I got into that lift and we went up," laughed Yerolemou.

Taua was thrilled at the response to today's free-entry birthday treat.

"Everyone seems to be having a good time ... we're really happy," Taua said.

About the Sky Tower

It is the 23rd tallest tower in the world and the tallest freestanding structure in the Southern Hemisphere.

Its total height is 328m. The top floor is located 222m up.

The tower took two years and nine months to build, including:
- 15,000 cubic metres of concrete
- 2000 tonnes of reinforcing steel
- 660 tonnes of structural steel

The tower cost $76 million to build.

Watch a promotional video for the Sky Tower from 1997 below.

Zoe Yerolemou of the UK discovered a fear of heights. Photo / Chris Loufte

Hundreds of people queued to go up the Tower. Photo / Chris Loufte.