A Len Lye sculpture on Wellington's waterfront that cost more than $1 million to install has been broken by a man swinging on it.

A Wellington city council spokesperson said the man had been injured and taken to hospital.

She said the council is working with police over the incident, and the area has been cordoned off.

The council said what happened is very disappointing.

The sculpture cost more than $1m to be installed in 2006, Wellington mayor Justin Lester said.

He had seen the video and said there had been problems with people climbing on the Wind Whirler for years.

"Which has caused quite a number of malfunctions and unfortunately today is the last example of someone behaving really inappropriately, and in fact snapping it off."

He said the man's behaviour was "silly".

Len Lye was one of the world's best kinetic artists, Mr Lester said, and had spent a lot of time in Wellington.

The city had wanted to recognise his work and the Water Whirler being one of his original designs.

Photo: Rebekah Parsons-King

"It's an important part of art and culture here in Wellington, but actually for the entire country," the mayor said.

It was unfortunate it had been besieged by problems, with the public climbing on it.

It was too soon to say how much the sculpture would cost to fix, but the council would try and get it fixed.

"We might be having chats to the individual involved just to see how we end up paying for this.

The police said the man was in a moderate condition in Wellington Hospital.

"I'm glad the individual is being looked after in hospital, but we would prefer it if people didn't climb on it," said Mr Lester.

It was also too soon to say whether charges would be pressed against the man.

The council said the sculpture, known as the Water Whirler, was not turned on as maintenance was being done on it.