Auckland's Sky Tower celebrates 25th birthday

 It's the defining landmark of New Zealand's biggest city, and Auckland's Sky Tower is celebrating its 25th birthday.

Despite the initial controversy around its planning and conception, it's become an icon of Auckland's skyline and our most visited tourist attraction.

It's hard to picture Auckland's skyline without the Sky Tower.

For 25 years, the 328m high needle has been lighting up the night skies to mark important occasions.

And the tallest free-standing structure in the southern hemisphere plays an important role in attracting tourists.

"We have over half a million visitors a year and we're really looking forward to the next 12 months and building that up with the help of international travel," SkyCity COO Callum Mallett told Newshub.

The Sky Tower is one of the largest commercial projects of its time – costing a total of $85 million.

Construction started in 1994 and was completed two years and nine months later - ahead of schedule.

Its concrete design attracted plenty of criticism.

"'A sewer pipe in the sky' I think was the reference in the paper," architect Gordon Moller told Newshub

But it's never bothered Moller.

"As it evolved and the pod came into shape, it started to reveal its true shape and at that point, people started to think about it a bit differently. Some people still don't like it I'm sure."

And it wasn't just its appearance that upset critics, but its association with the SkyCity Casino complex. Its association with gambling is still a point of contention.

Problem Gambling Foundation CEO Paula Snowdon said SkyCity Casino has a lot of pokie machines for people to use.

"The largest offering in Sky is pokie machines and there's a reason for that. They're the things that people are most addicted to and 60 percent of the harm in NZ is pokie machines."

But 25 years on, the visual landmark is still standing strong.